London woke to rain.

Not the soft kind — the heavy, metallic kind that made the city feel like it was bracing for something. The Thames churned under the bridges. Buses hissed through puddles. Commuters hunched into their coats, unaware that the city’s first coordinated covert attack in decades was minutes away.

Deep beneath Charing Cross, Jake, Emma, and Mercer moved through the abandoned Cold War bunker — a labyrinth of rusted doors, peeling paint, and old generator rooms that smelled of dust and forgotten secrets.

Mercer sat at a makeshift workstation, fingers trembling as he typed. “I’ve cracked another layer of the Sleeper Grid encryption.”

Emma leaned over his shoulder. “What does it show?”

Mercer swallowed. “Activation patterns. Timers. Locations.”

Jake stepped closer. “Locations where?”

Mercer hesitated. “London.”

Emma’s voice tightened. “Where in London?”

Mercer pointed at the screen.

A map of the city appeared — red dots pulsing across it like a heartbeat.

One at King’s Cross.
One at Oxford Circus.
One at Canary Wharf.
One at London Bridge.
One at a location that made Jake’s stomach drop.

“Southbank,” he whispered.

Emma’s eyes widened. “That’s where we first saw Mercer.”

Mercer nodded. “Helix has been preparing this for years. Sleeper units embedded in the city. Ordinary people with extraordinary access.”

Jake frowned. “Ordinary people?”

Mercer zoomed in on one of the dots.

A name appeared.

UNIT 12 — STATUS: ACTIVE
COVER: TFL SIGNAL ENGINEER

Emma whispered, “They’re using civilians.”

Mercer shook his head. “Not civilians. Assets. Recruited. Groomed. Planted.”

Jake clenched his fists. “What’s the objective?”

Mercer typed rapidly. “I don’t know yet. But whatever it is… It’s starting now.”

A shrill alarm blared from the console.

Emma jumped. “What is that?”

Mercer’s face drained of colour. “A trigger.”

Jake leaned over him. “A trigger for what?”

Mercer whispered, “The first attack.”

London Bridge Station — 08:14

The station was packed.

Commuters poured through the concourse, coffees in hand, headphones in, eyes glazed with morning fatigue. A TFL engineer in a high‑vis jacket walked calmly along the platform edge, toolbox in hand.

He wasn’t sweating.
He wasn’t nervous.
He wasn’t rushing.

He was waiting.

A train approached — headlights cutting through the tunnel.

The engineer reached into his toolbox.

Not for a wrench.

For a small black device with a blinking green light.

He placed it on the track.

The green light turned red.

He stepped back.

And smiled.

Charing Cross Bunker

Mercer’s voice cracked. “Jake… the first unit is active.”

Emma grabbed his arm. “Where?”

Mercer stared at the screen. “London Bridge.”

Jake didn’t hesitate. “We move.”

He grabbed his jacket, checked his weapon, and sprinted toward the exit tunnel.

Emma followed. “Jake, we can’t get there in time.”

Jake didn’t slow down. “We have to try.”

Mercer shouted after them. “It’s not just London Bridge! Multiple units are activating!

Jake stopped.

Turned.

“What?”

Mercer pointed at the map.

Red dots were turning black.

One by one.

UNIT 47 — ACTIVE
UNIT 12 — ACTIVE
UNIT 301 — ACTIVE
UNIT 88 — ACTIVE

Emma whispered, “This is coordinated.”

Mercer nodded. “This is Helix.”

Jake’s voice was low. “What’s the target?”

Mercer typed furiously. “I don’t know. It’s encrypted. But whatever it is… It’s big.”

Emma stepped beside Jake. “We need to warn MI5.”

Jake shook his head. “Harris controls the comms. He’ll intercept it.”

Mercer looked up. “Then we warn the city.”

Jake frowned. “How?”

Mercer pointed at the old Cold War radio console. “This bunker has an emergency broadcast system. It was designed to override civilian channels in the event of a nuclear strike.”

Emma’s eyes widened. “Can you activate it?”

Mercer nodded. “Yes. But once I do… Helix will know exactly where we are.”

Jake didn’t hesitate. “Do it.”

Mercer took a deep breath.

And pressed the button.

London Bridge Station — 08:16

The train screeched into the station.

The device on the track blinked red.

The engineer stepped back.

A voice crackled over the station speakers — distorted, urgent, unfamiliar.

“This is an emergency broadcast. Evacuate the station immediately. This is not a drill. Move. Now.”

The engineer froze.

His eyes widened.

He reached for the device—

Too late.

A security guard tackled him to the ground.

The device detonated.

Not a bomb.

A signal jammer.

The train’s braking system failed.

Screams filled the station.

The train hurtled toward the platform—

And at the last second, emergency buffers deployed, slamming into place with a thunderous crash.

The train screeched to a halt inches from the crowd.

Silence.

Then chaos.

Charing Cross Bunker

Mercer sagged in his chair. “We stopped it. We actually stopped it.”

Emma exhaled shakily. “One attack.”

Jake stared at the map.

More dots were turning black.

More units are activating.

More threats are waking up.

He whispered, “This is just the beginning.”

Emma stepped beside him. “Jake… what do we do?”

Jake looked at the map — at the city he’d sworn to protect — now under silent siege.

“We find Helix.”

He clenched his fists.

“And we end the Sleeper Grid.”