The Wi-Fi Never Lies
Will was sitting in his home office.
He’d bought the house a few months earlier, after his wife had died, leaving him alone with their three-month-old son.
He couldn’t bear to stay in the flat they’d shared for five years. Everywhere he looked, Sarah was still there. Her mug in the cupboard. Her shampoo in the bathroom. The dent in the sofa where she used to curl up beside him.
The cries of his son when he was wet, hungry, or simply mad with the world didn’t fill the silence left by Sarah’s missing laughter.
Jamie was asleep in the little bassinet beside the desk, burbling contentedly after a bottle of formula and a fresh nappy.
Will looked down and smiled sadly.
Just you and me, kid.
He reached down and gently stroked the soft hair on the boy’s head.
“Miss you, Sarah,” he said to no one in particular.
Then he looked back at his computer.
A new application’s dashboard filled one of the screens.
Will had become slightly obsessed with security since Sarah’s death.
The police had called it a burglary gone wrong.
Someone had entered the old flat late one evening while Will was out. A neighbour had heard raised voices and called the police. By the time they arrived, whoever had been there had gone.
Sarah had been found at the bottom of the stairs.
The assumption was that she’d fallen during a confrontation.
No one had been caught.
For the first few hours, the police had treated Will as a possible suspect. He was the husband. He’d been out late. There had been an argument.
Fortunately, technology had proved otherwise.
Their video doorbell had recorded him leaving. A petrol station camera had caught his car. The supermarket had CCTV of him wandering around the freezer aisle, staring at different tubs of ice cream.
Sarah had developed a taste for expensive chocolate fudge brownie during pregnancy.
Three months after giving birth, the craving hadn’t gone away.
“It’s your fault,” she’d told him.
“How is it my fault?”
“You got me pregnant.”
“Technically, I think we both contributed.”
“You didn’t have to carry him.”
“Fair point.”
She’d kissed him and sent him out.
That had been the last time he’d seen her alive.
The new house was different.
Cameras inside and out. A video doorbell. Another camera watching the drive. Reinforced external doors. Security glass. Window sensors. Motion detectors. An upgraded alarm system.
Probably too much.
Will knew that.
But he also knew what it felt like to lose almost everything because somebody had managed to get through a locked door.
Everything was there to protect the one thing Sarah had left behind.
Jamie.
The new application wasn’t really part of the security system.
It was something extra.
Will had found the project online a couple of weeks earlier and had become fascinated by the idea.
With a handful of cheap sensors positioned around the house, the software claimed it could detect people by measuring the way their bodies disturbed Wi-Fi signals.
No cameras.
No microphones.
No wearable devices.
Just radio waves.
The principle made sense.
His router already filled the house with Wi-Fi. Every wall, chair, cupboard and person affected how those radio waves travelled. Move through them and the reflections changed. Sit still and even breathing could alter the signal slightly.
With the right hardware, enough receivers and sufficiently clever software, those changes could supposedly be interpreted.
It sounded almost ridiculous.
Which, of course, meant Will had to try it.
The Raspberry Pi had originally been a media box. It lived beside the router, quietly serving films and music to the television and anything else on the network that asked nicely.
When Will found the Wi-Fi sensing project, it seemed easier to give the Pi another job than leave his main computer running all day.
The sensing service ran in the background.
The dashboard itself was just a web page he could open from his computer, phone or tablet.
That meant he could walk through the house and watch the system follow him.
He’d installed three sensor boards initially.
Then four.
Then five.
The first evening had been entertaining.
The dashboard showed a simple floor plan of the house. Each detected person appeared not as a dot, but as a dark, semi-transparent shape, roughly human in outline.
A shadow.
When someone moved, the shape shifted across the floor plan, smearing slightly at the edges before resolving again.
Will carried Jamie into the office.
OFFICE: 2
TOTAL OCCUPANCY: 2
He put Jamie down and walked into the hall.
On his phone, one shadow stayed in the office.
The other followed him.
OFFICE: 1
HALLWAY: 1
TOTAL OCCUPANCY: 2
He stepped into the kitchen.
OFFICE: 1
KITCHEN: 1
TOTAL OCCUPANCY: 2
Will grinned.
“Very clever.”
A few minutes later he carried Jamie upstairs.
Two shadows moved together along the landing.
He put Jamie into the cot in the nursery and returned downstairs.
NURSERY: 1
LIVING ROOM: 1
TOTAL OCCUPANCY: 2
For something assembled from inexpensive development boards and open-source software, it was remarkably good.
Three nights later, Jamie started crying just after two in the morning.
Will woke on the sofa with the television still muttering quietly to itself.
His phone was on the coffee table beside him.
The occupancy dashboard was still open.
Three shadows.
One in the living room.
One in the nursery.
One moving quickly up the stairs.
Will frowned.
He was the one in the living room.
Jamie was in the nursery.
The third shadow reached the landing, crossed into the nursery and stopped beside the cot.
Jamie kept crying.
Will sat very still.
On the baby monitor, his son kicked angrily beneath the blanket, face screwed up and red.
Nothing else appeared on the screen.
The shadow on the occupancy map remained beside him.
Will tapped it.
A diagnostics page opened.
SIGNAL DETECTED
RESPIRATION: NONE
HEARTBEAT: NONE
He checked the baby monitor again.
Nothing.
“No breathing. No heartbeat.”
He refreshed the page.
The shadow remained.
“Must be a glitch.”
Multipath. Reflections. Some odd radio artefact the software had decided looked enough like a person to draw one.
That was all.
Jamie’s crying became louder.
“All right, mate.”
Will picked up his phone and went upstairs.
As he entered the nursery, the display changed.
The third shadow disappeared.
NURSERY: 2
TOTAL OCCUPANCY: 2
Will lifted Jamie from the cot.
“See? I’m here.”
The crying gradually subsided.
Will glanced at the phone again.
Two occupants.
Just him and Jamie.
His parents visited that weekend.
His mother, Margaret, arrived with enough food to survive a siege.
His father arrived carrying a small case of test equipment.
Richard had been an electronics engineer for most of his working life. He had started out repairing and designing audio equipment, back when circuit diagrams came folded inside service manuals and faults were found with an oscilloscope rather than a firmware update.
Later he’d moved into industrial electronics.
Retirement had not stopped him taking things apart.
Nor playing with amateur radio.
His shack in the spare bedroom still contained a transceiver, antenna tuner, soldering station, an old analogue SWR meter and enough test equipment to investigate most things that annoyed him.
The closest thing Richard and Margaret had to a smart home was the video doorbell Will had bought them for Christmas.
Richard had objected.
“I’ve got a perfectly good doorbell.”
“It doesn’t show you who’s standing outside.”
“I can open the door.”
“That’s rather the point I’m trying to avoid.”
Margaret had sided with Will.
That had settled it.
Richard stood in Will’s hallway now, looking up at one of the cameras.
“You’ve gone a bit overboard.”
“I know.”
“Do you?”
“Probably.”
Margaret took Jamie from him.
“Ignore your father. We’re going out.”
“We are?”
“Your son and I are. You two can play with your toys.”
Richard looked offended.
“They’re instruments.”
Margaret kissed Will on the cheek.
“Couple of hours. You need a break.”
Will watched her leave with Jamie in the pram.
Richard followed him into the office.
“So,” he said, “show me your magic ghost detector.”
“It’s not a ghost detector.”
“Good.”
“It measures changes in the Wi-Fi field.”
“Reflections?”
“Among other things.”
Richard nodded.
“That bit I believe.”
Will smiled.
“And the rest?”
“The rest sounds like a very complicated way of discovering you’ve walked into a room.”
They spent the next hour testing it.
Will stayed in the office while Richard wandered around the house.
OFFICE: 1
KITCHEN: 1
TOTAL OCCUPANCY: 2
Richard stepped out of the kitchen and into the hallway.
OFFICE: 1
HALLWAY: 1
TOTAL OCCUPANCY: 2
The shadow moved with him.
He went upstairs.
OFFICE: 1
LANDING: 1
TOTAL OCCUPANCY: 2
Richard stood perfectly still for nearly a minute.
His shadow remained on the landing.
“That’s actually quite impressive,” he admitted.
Then he walked into the spare bedroom.
The shadow followed.
Will watched it cross the floor plan.
“You realise you’re enjoying this.”
“I’m verifying it.”
“Of course you are.”
Richard came back downstairs and noticed a plug beside the desk.
“What’s that?”
“Powerline adapter.”
Richard stared at him.
“You’re using powerline networking?”
“Only for the office.”
Richard looked genuinely pained.
“You’re trying to measure tiny changes in reflected radio signals while deliberately pumping data through a few hundred metres of mains wiring inside the walls?”
“It shouldn’t matter.”
“Shouldn’t is doing some heavy lifting there.”
He unplugged it.
“Your LED lights are filthy too.”
“They were here when I moved in.”
“That doesn’t make them less filthy.”
Richard checked power supplies, signal levels and Wi-Fi channels. He connected a small spectrum analyser and spent several minutes complaining about the amount of radio noise produced by modern household electronics.
Eventually he sat back.
“Nothing obviously wrong.”
Margaret returned shortly afterwards.
Will heard the front door open and immediately forgot about the experiment.
He went downstairs.
Jamie was awake and furious about something.
Will lifted him from the pram.
“Hello, trouble.”
By the time he’d changed him, fed him and listened to Margaret explain in detail how many people had admired him in the park, Richard had packed most of his equipment away.
Will didn’t look at the occupancy display again until after his parents had gone.
OFFICE: 2
HALLWAY: 1
TOTAL OCCUPANCY: 3
Will.
Jamie.
And someone in the hallway.
Rachel visited the following week.
She had known Sarah since college, though friend had stopped being quite the right word years ago.
After Sarah’s parents died, Rachel’s family had simply begun including her.
A place at Christmas.
A birthday present.
Sunday lunch.
Nobody had formally discussed it.
Sarah had become family.
By the time Sarah met Will, Rachel introduced her as her sister often enough that nobody bothered correcting her.
Rachel was Jamie’s Auntie Rachel in everything except blood.
She stood in the hallway and slowly looked around.
The camera above the front door.
Another covering the stairs.
A small black dome in the corner of the ceiling.
Then she entered the living room.
Her eyes moved across the photographs on the mantelpiece.
Sarah between her mum and dad at graduation.
Sarah with Rachel and her parents at a summer barbecue a few years later.
Will and Sarah on their wedding day, Rachel beside the bride and Rachel’s parents smiling from the front row.
And, at the end, Sarah holding Jamie.
Rachel looked at that one for a little longer.
Then she looked at Will.
“Sarah wouldn’t let you get away with all these cameras.”
Will managed a smile.
“No.”
“She’d have made you take half of them down.”
“Probably.”
“Definitely.”
Rachel glanced towards the camera above the bookcase.
“She hated being watched.”
Will looked at her.
Rachel seemed to realise she’d said something more important than she’d intended.
“What?”
“Nothing.”
“No. What did you mean?”
She hesitated.
“Just Daniel.”
Will frowned.
“Mercer?”
“Yeah.”
“Her old boyfriend. Bit of a wanker, she would say.”
Rachel gave a short laugh.
“That’s one way of putting it.”
“She told me he was controlling.”
“He was.”
“How controlling?”
Rachel sat down.
For a moment she looked towards the graduation photograph.
“Did she ever tell you about the tracking app?”
“What tracking app?”
That answer seemed to bother Rachel.
“When we were at college. Daniel worked for a security company. He was doing some kind of electronics course one day a week. He set this location thing up on Sarah’s phone so her mum and dad could see where she was.”
“Why?”
“Safety. That’s how he sold it. Sarah was eighteen. Her parents thought it was sensible.”
“They could track each other?”
“Yeah. Sarah, her mum, her dad. All three.”
“So?”
“So Daniel set it up.”
Will waited.
Rachel looked down at her coffee.
“And he kept access.”
“How do you know?”
“We didn’t. Not then.”
She looked back at him.
“He just always knew where she was.”
Will felt the first small movement of unease.
“Sarah never told me that.”
“Sarah didn’t tell people half the things Daniel did. Not once she’d got away from him.”
Rachel explained.
Mercer had been twenty-two when he met Sarah.
Sarah was eighteen, finishing her A-levels.
Mercer was already working for an electronic security company and attended college one day a week.
He had money.
A car.
Confidence.
He knew pubs where nobody looked too closely at ID.
At first, everyone liked him.
That was the part Rachel remembered most clearly.
“If he’d been horrible from day one, she’d never have gone out with him.”
The controlling behaviour arrived gradually.
Where are you?
Who are you with?
Why didn’t you answer?
I’ll pick you up.
You don’t need to go there without me.
By twenty-one, Sarah had had enough.
Peter and Alison Hayes had supported her when she finally ended things with Mercer.
He didn’t take it well.
For months afterwards he would appear unexpectedly.
Outside college.
At a café.
Once at a pub when Sarah had gone out with Rachel.
Another time outside a restaurant.
Sarah eventually threatened to involve the police.
The appearances mostly stopped.
A couple of years later, her parents were killed in a car crash.
Will knew that part of Sarah’s life well enough.
She’d told him about the knock on the door.
The hospital.
The funeral.
How suddenly she’d found herself with no immediate family left.
But she’d never connected it to Mercer.
Rachel went quiet.
Will noticed.
“What?”
She looked at him.
“Will… you don’t know, do you?”
“Know what?”
Rachel glanced towards the graduation photograph.
“Daniel was driving the car that killed them.”
For a moment Will thought he’d misunderstood her.
“What?”
“Mercer.”
“No.”
“Yes.”
“Sarah would have told me.”
Rachel’s expression was sad rather than surprised.
“No. Sarah told you her parents died in a car crash. She told you Daniel had been her controlling ex.”
Will said nothing.
“She just never told you those were the same story.”
He looked at the photograph again.
“Why?”
“Because she’d survived it.”
Rachel paused.
“And because I think she wanted Daniel Mercer to take up as little space in the rest of her life as possible.”
Will looked back at her.
“You said she thought he knew where they were.”
Rachel nodded.
“She never believed the crash was just bad luck.”
“She thought he followed them?”
“No. She thought he didn’t need to.”
Will understood before she said it.
“The app.”
“It moved with their phones. Every time they upgraded, they transferred everything. Nobody thought about it. Why would they? It was a security app.”
“And Mercer still had access.”
“We think so. Through the web portal. Or the desktop client. His work laptop.”
Rachel folded her arms.
“The phones were the things being tracked. Nobody thought about the machine being used to watch them.”
Mercer had initially denied being anywhere near the restaurant where Peter and Alison had eaten that evening.
A witness later reported seeing his car nearby.
He was charged following the collision and eventually went to prison.
“His company wiped his laptop when he was sent down,” Rachel said.
“How do you know that?”
“Sarah found out afterwards. Standard process. Employee leaves, accounts disabled, kit wiped.”
The strange appearances had stopped because Mercer had lost his window into their lives.
Rachel looked towards the graduation photograph again.
“You knew what happened, Will. Sarah just never told you all the things that happened before it.”
Will stared at Sarah’s smiling face.
“She wanted that to be the end of the story,” Rachel said.
That evening Will searched Daniel Mercer.
The first few results were irrelevant.
Then he found the photograph.
Mercer, younger, being escorted down the steps of a Crown Court.
DRIVER JAILED AFTER COUPLE KILLED IN NIGHT-TIME COLLISION
Will clicked it.
Peter and Alison Hayes.
The names stared back at him.
Another result.
MAN ADMITS CAUSING DEATHS OF FORMER GIRLFRIEND’S PARENTS
Mercer had pleaded guilty to two counts of causing death by careless driving.
His barrister had described the collision as a tragic moment of inattention.
Will stared at the phrase.
A tragic moment of inattention.
Two people dead.
Another article had been published several years later.
DRIVER FREED AFTER FATAL CRASH SENTENCE
There was a photograph of Sarah outside court.
Arms folded.
Furious.
The article quoted her saying that she did not believe the collision had been accidental.
Will read it twice.
Then a third time.
He barely slept.
The pattern with the Wi-Fi system became impossible to ignore.
When Jamie was in the house, the extra shadow appeared.
When Jamie wasn’t, it didn’t.
His parents offered to have Jamie for two nights.
“You need sleep,” Margaret told him.
“I sleep.”
“No. You lie down occasionally.”
Will resisted.
Eventually he agreed.
The first night alone, the house felt enormous.
He checked the occupancy system.
OFFICE: 1
TOTAL OCCUPANCY: 1
Later:
BEDROOM: 1
TOTAL OCCUPANCY: 1
At three in the morning:
BEDROOM: 1
TOTAL OCCUPANCY: 1
The next day:
One.
When his parents brought Jamie home, Will carried him inside.
HALLWAY: 2
TOTAL OCCUPANCY: 2
A few minutes later:
LIVING ROOM: 2
HALLWAY: 1
TOTAL OCCUPANCY: 3
Will stared at the third shadow.
It moved through the hall.
Stopped beneath the camera.
Then went into the living room.
Stopped beneath that camera too.
Kitchen.
Camera.
Stairs.
Camera.
Finally, it went upstairs.
Towards Jamie.
Will called his father.
Richard returned the following Saturday.
This time he brought more equipment.
By then Will had stopped trying to convince himself the additional detections were random.
He hadn’t told Richard what he’d discovered.
Richard connected the spectrum analyser, checked the sensors, tested the power supplies and made Will switch off the powerline networking entirely.
They recalibrated the system.
“Nothing obviously wrong,” Richard said.
“Can we try something?”
Richard looked at him.
Will lifted Jamie from the play mat.
“I’m going to take him out.”
“Where?”
“Doesn’t matter.”
Richard frowned.
Will put Jamie into his coat, settled him into the carrier and left through the front door.
Richard remained inside.
For nearly half an hour, the dashboard behaved impeccably.
OFFICE: 1
TOTAL OCCUPANCY: 1
Richard walked into the kitchen.
KITCHEN: 1
TOTAL OCCUPANCY: 1
Upstairs.
LANDING: 1
TOTAL OCCUPANCY: 1
He returned to the office.
Then Will’s voice came through the video doorbell downstairs.
“I’m back.”
Richard heard the lock turn.
The front door opened.
OFFICE: 1
HALLWAY: 1
TOTAL OCCUPANCY: 2
Will stepped inside.
A moment later the system separated the smaller second body he was carrying.
OFFICE: 1
HALLWAY: 2
TOTAL OCCUPANCY: 3
Richard smiled despite himself.
“Got the little one too.”
Then another shadow appeared.
OFFICE: 1
HALLWAY: 3
TOTAL OCCUPANCY: 4
Richard’s smile disappeared.
The new shadow stood just behind Will and Jamie.
Richard clicked it.
SIGNAL DETECTED
RESPIRATION: NONE
HEARTBEAT: NONE
“Will?”
No answer.
Downstairs, Will was talking softly to Jamie as he took off the boy’s coat.
The shadow moved towards them.
Will appeared in the office doorway a moment later.
“Well?”
Richard looked at him.
Then back at the screen.
“Take him out again.”
Will’s expression changed.
“You saw it.”
“Take him out again.”
They repeated the test.
Then again.
Richard alone:
One.
Will and Jamie returning:
Three.
Then four.
Every time.
On the third attempt, a second unexplained shadow appeared near the front door.
TOTAL OCCUPANCY: 5
Richard sat very still.
Will waited.
Eventually he said, “Well?”
Richard took off his glasses and rubbed the bridge of his nose.
“I can tell you what it isn’t.”
“What?”
“It’s not your powerline adapters.”
Will almost laughed.
“It’s not the sensors. It’s not an obvious transmission from next door. It’s not one bad receiver because they’re all seeing it.”
“So what is it?”
Richard looked at the dark shapes on the floor plan.
“I didn’t say I could tell you that.”
Over the following weeks, the number occasionally rose again.
Three.
Four.
Five.
Never when Jamie was away.
Will began to notice patterns.
One shadow checked the cameras.
Another seemed obsessed with the doors.
The third spent an extraordinary amount of time in the kitchen.
He told Rachel.
Not immediately.
Only after Richard had repeated the tests enough times that Will could no longer convince himself he was imagining things.
Rachel came round one afternoon.
Jamie was upstairs asleep.
The dashboard showed six occupants.
Three were easy to account for.
Will.
Rachel.
Jamie.
The other three were not.
Rachel stared at the tablet.
“What am I looking at?”
“The system thinks there are six people in the house.”
“There are three.”
“I know.”
One shadow was near the front door.
It moved to the back door.
Paused.
Then returned to the front.
Rachel’s expression changed.
“What?”
She didn’t answer.
“Rachel?”
“Peter.”
Will looked at her.
“What about him?”
“Sarah’s dad. He used to do that.”
“Do what?”
“Check the front door. Then the back. Then the front one again because he’d convinced himself he’d forgotten.”
Will looked at the tablet.
The shadow remained beside the front door.
Another shadow was in the kitchen.
It moved from one side of the room to the other, paused, then moved back again.
Rachel gave a small, sad smile.
“Maybe that one’s Alison.”
“Why?”
“No one went hungry or thirsty in that house. Alison would have the kettle on and the biscuits out by the time Peter opened the front door.”
Will looked towards the kitchen.
Empty.
On the screen, the shadow continued to move quietly around it.
The third shadow left the upstairs landing.
It moved slowly past the camera.
Stopped beneath it.
Then continued towards the nursery.
Rachel watched.
“Sarah wouldn’t like those cameras.”
Will said nothing.
The shadow entered the nursery and stopped beside Jamie.
Rachel looked at him.
Neither of them said the name.
There were no cold spots.
No voices.
No mist.
No objects moving by themselves.
The cameras recorded nothing unusual.
The baby monitor showed only Jamie.
The only evidence was data.
That was almost worse.
Rachel called one evening.
“I’ve remembered something.”
“What?”
“Sarah saw him again.”
Will sat upright.
“Mercer?”
“After he got out.”
“When?”
“Not straight away.”
Rachel hesitated.
“When she was pregnant.”
Will felt his stomach tighten.
“She didn’t tell me.”
“She didn’t want you worrying.”
“What happened?”
“Nothing. She saw him once near work. Then he messaged her from some new account.”
“What did he say?”
“Mostly just that he wanted to talk.”
“Mostly?”
“He said he’d heard about the baby.”
Will closed his eyes.
“Why didn’t she go to the police?”
“Because he hadn’t actually done anything. Not then. And she thought if she ignored him he’d get bored.”
Rachel’s voice became quieter.
“Will, I think she was frightened of him. She just didn’t want him deciding how she lived her life again.”
Will went back through everything he had from the night Sarah died.
Police statements.
Emails.
The neighbour’s account.
He’d read them all before, but grief had turned most of the words into noise.
Now he saw things differently.
The neighbour hadn’t reported sounds of a burglary.
She had reported an argument.
A woman’s voice.
A man’s voice.
Then a loud crash.
By the time police entered, there was no one else inside.
The back door was open.
A drawer in the living room had been pulled out.
A jewellery box had been disturbed.
Nothing significant appeared to have been stolen.
Burglary interrupted.
Homeowner confronted intruder.
Fall during struggle.
Reasonable.
Simple.
Will looked at the Wi-Fi display.
NURSERY: 2
KITCHEN: 1
HALLWAY: 1
LIVING ROOM: 1
TOTAL OCCUPANCY: 5
Jamie was asleep upstairs.
Will was alone downstairs.
Three impossible shadows moved quietly through the house.
“Sarah?”
The shadow beside the nursery cot didn’t move.
Will felt ridiculous.
He closed the browser.
Three nights later, the alarm didn’t go off.
That was the first thing he noticed afterwards.
The system had been armed.
Every door sensor active.
Every camera recording.
Yet at 1:17 a.m., Will’s phone vibrated.
Not the alarm.
The Wi-Fi sensing system.
NEW SIGNAL DETECTED
Will opened the dashboard.
TOTAL OCCUPANCY: 6
He stared at the screen.
Five had become normal.
Will.
Jamie.
And the three shadows.
Now there were six.
One shape was outside the rear of the house.
Moving.
Will opened the garden camera.
Nothing.
The shadow crossed the patio.
Reached the kitchen.
Then appeared inside.
No alarm.
No door notification.
Will’s mouth went dry.
He switched to the kitchen camera.
A man moved briefly through the edge of the frame.
Will stopped breathing.
Mercer.
Older.
Heavier.
But unmistakable from the photographs.
Will grabbed his phone and dialled 999.
Then he ran upstairs.
Jamie was asleep.
Will lifted him from the cot and carried him into the bedroom.
He locked the door.
On the tablet, the occupancy map continued updating.
Mercer’s shadow moved from the kitchen into the hallway.
The others changed position.
The one Rachel had identified as Peter left the front door.
The one she believed was Alison left the kitchen.
The third moved away from the nursery.
Will watched.
For weeks they had drifted through familiar routines.
Now they weren’t drifting.
They were converging.
Mercer reached the staircase.
The hallway camera showed him looking upwards.
He had something in his hand.
Will couldn’t see what.
On the Wi-Fi display, three dark figures surrounded him.
Mercer froze.
The camera showed him turning sharply.
Looking behind him.
There was nobody there.
He took one step backwards.
Then another.
His mouth moved.
Will couldn’t hear what he said.
One of the shadows moved towards him.
Mercer stumbled.
Recovered.
Another closed in.
He backed onto the first stair.
The camera showed him staring at empty space.
Then he jerked violently sideways.
His foot missed the step.
He fell.
The sound carried through the house.
Mercer struck the stairs once, twice, then landed heavily at the bottom.
Will stared at the camera.
Mercer didn’t move.
The occupancy count stayed the same.
TOTAL OCCUPANCY: 6
Will opened the diagnostics.
The shadow at the bottom of the stairs still registered.
SIGNAL DETECTED
RESPIRATION: NONE
HEARTBEAT: NONE
For several seconds, nothing happened.
Then the shadow moved.
Will leaned closer.
The camera still showed Mercer’s body lying at the foot of the stairs.
But on the floor plan, the dark human shape rose from exactly the same position.
It stood.
Then moved quickly towards the front door.
The other three followed.
Mercer’s shadow crossed the hallway.
Peter’s behind it.
Alison’s next.
Then Sarah’s.
The first disappeared beyond the edge of the house.
The count dropped.
TOTAL OCCUPANCY: 5
Then another disappeared.
TOTAL OCCUPANCY: 4
Then another.
TOTAL OCCUPANCY: 3
Will stared at the screen.
Three.
Him.
Jamie.
And one other.
The final shadow had stopped.
It turned away from the front door.
Then moved upstairs.
Slowly.
Towards the nursery.
Will opened the baby monitor.
Empty cot.
Of course.
Jamie was in his arms.
The shadow entered the nursery anyway.
It stopped beside the cot.
Will felt tears running down his face.
He said nothing.
After a while, the shadow moved.
Out of the nursery.
Along the landing.
Down the stairs.
Past the cameras.
Towards the front door.
Then it disappeared.
TOTAL OCCUPANCY: 2
Will looked down at his son.
Jamie slept against his chest.
Outside, sirens were approaching.
Postscript
Years later, Will stood at the front window and watched Jamie walk down the path in his school uniform.
Jamie was nearly at the gate when he turned and waved.
Will waved back.
Then the boy was gone.
The house felt unusually quiet.
Will carried his coffee into the office and sat down at the desk.
The Raspberry Pi was still running.
The sensing system had changed over the years, been updated, rebuilt, ignored and occasionally rediscovered.
Will hadn’t opened the occupancy dashboard in months.
For a moment he simply looked at the bookmark.
Then he clicked it.
The floor plan appeared.
OFFICE: 1
TOTAL OCCUPANCY: 1
Will smiled faintly.
“Just me, then.”
He took a sip of coffee.
A second shadow appeared in the hallway.
Will stopped.
The shadow moved towards the front door.
Paused beneath the camera.
Then the living room.
Another pause.
The kitchen.
The stairs.
Camera after camera.
Will was smiling before it had even reached the office.
The shadow entered.
It stopped beside his chair.
OFFICE: 2
TOTAL OCCUPANCY: 2
“Hello, Sarah.”
Will leaned back.
“Can’t leave me on my own?”
The second shadow remained beside him.