Vikram’s hockey stick is braced against his throat. The boy struggles, twists and tries to unbalance him. He puts up a better fight than I did. Then he reaches up, almost lazily, and slaps Vikram in the side of the neck. It seems too much of a glancing blow to hurt but Vikram falls back clutching his throat.

There’s something in the boy’s hand. A knife? Vikram leans against the wall, his eyes wide and terrified. Even on the grainy screen I see the blood pulsing through the gaps in his fingers.

Another shape moves into frame, obscuring him.

Jonah.

He has Marcus by the scruff of his neck, his hunting knife pointing straight up against the underside of his chin. Marcus’s eyes swivel in their sockets in a vain and ill-advised effort to catch a glimpse of the knife. Jonah presents him to the camera like a sacrifice.

Open up or else, his grin says.

“Don’t open it,” Farah says quickly.

Benedict’s hand hovers over the switch. “I have to.”

There’s a snap of metal as he flicks the switch and a hollow clunk as the electromagnets give way and release the corridor. Noise bursts into the lab. Abi staggers in, swearing and shouting as Levi pushes her ahead of him. Vikram follows, his mouth open, struggling to breathe, his hands clamped to his neck.

A tray of Petri dishes clatters noisily to the floor. An office chair is knocked over. We stand rigid in the doorway, feeling like the world dropped out from beneath our feet. Benedict’s hand pulls my shoulder and I follow him back to the common room.

The sofas.

The taped-off area.

Marcus’s trap.

I glance at Farah, Chiu and Benedict as we find our spots. Farah is closest to the switch. If they stand in the right place, she could—

Levi pushes Abi roughly on to the sofa next to us. She’s bleeding from a gash across her cheek, but Levi’s nose is broken and gushes blood and both eyes are beginning to blacken already. Good for her, I think.

Vikram crashes on to the sofa and rolls on to his back, still clutching his throat.

“You stabbed him! You stabbed him!” Marcus shouts hysterically. Jonah steps forward and slaps him and he sits down with a shocked expression on his face.

Ose comes in next. He’s got a cut on his head and a sullen look. Maybe Vikram managed to knock him out. Maybe he doesn’t like this part. Fighting and killing people, that’s Jonah’s style, not Ose’s. For Ose, it’s just the price of admission.

Behind Ose comes the new guy. Gaunt and lean, dressed in black T-shirt and black jeans, with a khaki-green rucksack. My stomach twists when I see him. I can’t explain it, but I know he’s the reason I wouldn’t go down that road, the reason I made us take such a long detour. He’s the person I sensed lurking in the shadows, waiting for us.

He’s just a kid, but he’s all wrong.

“You’re trespassing,” Benedict says, trying to keep his voice from trembling.

“I’m sorry,” Jonah says, lifting his hands in a calming gesture that’s undermined by the vicious-looking hunting knife he’s still holding. “You jumped us, we didn’t mean for anything… Oh, god! Is he OK?”

“You stabbed him!” Abi says, accusingly.

“We were defending ourselves,” Jonah says, his voice pleading.

It’s an act, I think. It’s not even a good act. But the others don’t know that. I spot a rapid exchange of looks between Benedict and the others. Jonah pauses, seems to notice the knife in his hand and makes a point of placing it carefully on the coffee table, backing away with his hands up and his eyes fixed on Benedict.

“I’m … I’m sorry… My name’s Jonah.”

All I see is violence and malice, a knife pressed against an old man’s chest, but Benedict nods slightly in return. A calmness is coming to the room, the adrenaline of battle ebbing away. Only Vikram, breathing tightly next to me, to remind us what just happened.

“You’re trespassing,” Benedict says again, more softly. “You need to leave.”

“Look, it’s OK,” Jonah says. “It’s OK, really. I’m Jonah. This is Levi. Kevin. Ose.”

Silence.

A flicker of impatience on Jonah’s face. He’s done his piece and now he’s expecting a response. He catches my eye and I know at once that he’s here for me. He’d kill the others in a second but maybe he’s trying to save himself the trouble. Or maybe, now he’s here, he’s figuring there might be other things of value he can lay claim to.

He waits, requiring an answer.

“I’m Dr Benedict Brownstein,” Benedict says, carefully. “This is my lab.”

“I’m sorry,” Jonah says again. “We didn’t mean for…” He turns to me and flashes me a look that’s filled with hurt. “We’ve been looking for him.”

Benedict glances at me, then back to Jonah. “What’s he to you?”

“We took the three of them in,” Jonah says. “Tried to help them. But … he murdered one of my friends and left. I don’t know why.”

“It’s a lie,” Farah says.

Benedict looks troubled. “Kyle?”

“I…” My voice trails off. I see Tongue’s questioning eyes, his hand reaching up and covering my own. I don’t need to say anything else; Benedict sees it in my face.

“It’s not true,” Farah insists. “He’s twisting it.”

It doesn’t matter. Benedict wants this over with. He wants to go back to his books and his theories. All he needs is an excuse to make everything OK.

“What do you intend to do now you’ve found him?” Benedict asks.

Jonah feigns a nervous laugh. The act is slipping now, he’s getting bored of it anyway. “Well … we have a situation, don’t we? I lost a good friend and I have a score to settle.”

Benedict looks down and stares thoughtfully at his hands. I can see him calculating, trading my life against the inevitable injury and death, the threat to his work.

“I don’t have any quarrel with you,” Jonah goes on. “Let me take the boy and we’ll get out your way. No foul, no harm. Forgive and forget and all that.”

Farah gives me a stark look, one that tells me she’s ready to launch herself at whoever’s closest the minute I give her the nod.

Jonah stands half in and half out of Marcus’s kill zone, one leg straggling the taped line on the floor. Levi is next to him, fully in. But Ose and the new guy are safe. Marcus is sitting on the very edge of his seat, waiting for Benedict to tell him what to do.

They’re scientists, I think. What would be the rational choice?

“I’d need your guarantee you wouldn’t harm him,” Benedict says, unconvincingly.

I don’t know why I’m important to Jonah, but if he cares so much maybe I have something to trade for everyone else’s lives after all. It doesn’t matter either way, I can’t let Benedict try to fight Jonah, even if he wanted to.