Will’s wail shivered through the room. I’d never heard him make a sound like it. Lizzie stopped hitting Grady and tried to get to Carmen, but Will blocked her with an outstretched arm and shoved her sprawling.

He raised his face to the monitors. “You must have a medical team on standby – send them in. Fix her!”

Gold ignored him.

My mind kept flicking back over the past three days, trying to understand. How was Grady anything like Will? Slowly, scenes gained clarity. No, I realized, Grady wasn’t like Will. He was better. Somehow, he’d got me to carry his rucksack for him. He was the one who stayed safely with Carmen while Will and I took the risks. He’d got out of every fight, avoided every difficulty. We hadn’t known Grady in Primary – he’d learned how to act long before he met us. Now he bumbled his way along, faking ineptitude, handing around those bags of sweets. All he cared about were his precious conspiracies.

Conspiracies… I kept staring at Carmen. I couldn’t see any blood. Where was she hurt? I blinked. This didn’t feel real. I caught my breath and took care to hide my face from the monitors. Of course – this wasn’t real! Will was faking his grief.

We’d fooled the door with the fake body parts, now Grady had fooled Gold with a fake murder. Will must have seen it instantly. Grady had come up with a solution. All we had to do was wait until someone came to take the winner to safety and we could rush them.

Will cried out again and pulled Carmen’s right hand to his cheek. When he released her fingers, it dropped to the floor with a thud.

Her acting was amazing. Maybe Carmen couldn’t be a vet any more, but she could get on TV. Will was laying it on a bit thick though. Gold wouldn’t believe this outpouring of emotion any more than I did.

I limped over to Will and put my hand on his shoulder, but Will shrugged it off violently.

“Ease off a bit,” I whispered, hoping the microphones in the room weren’t too sensitive. “He won’t buy it if you go over the top.”

Slowly Will lifted his eyes to mine, confusion in his expression. “Buy what?”

“This.” I gestured at Carmen and put my lips to his ear. “You’re hamming it up too much.” I pulled back and gave Will a tug. “Come on, bro, leave her be.”

Will said nothing. Instead he lifted his left hand and showed me the palm. It was covered in blood.

I frowned. “Where’s that coming from?”

I looked down and saw where he had been pressing on her chest. I jerked backwards as if I’d been stung. There was blood on her shirt – fresh blood. Without Will’s hand applying pressure, it was spreading, like an oil stain, over her chest and stomach.

“C-Car?” I started to tremble.

Lizzie glared poison at Grady. “You killed Carmen.”

“She deserved it.”

“You’ve killed us,” Lizzie choked.

“Yeah, well, it’s not like you ever did anything for me. Ben and Will were going to leave me out of their plan. They were trying to kill you a minute ago!”

“I wouldn’t have…” My hands were on Carmen’s chest now, helping Will as he tried to staunch the blood. I couldn’t feel a heartbeat. She was already gone, but neither of us could stop.

“Yes, you would,” Grady snapped. “You were.”

“What about me?” Lizzie clutched her elbows. “I was your friend.”

“Not one of you was my friend,” Grady yelled. “You only let me join you for Duke of Edinburgh because my dad made you. You laugh at me.” He calmed suddenly, as if a switch had been flicked and he was the same old Grady. “You never thought anything of me. Stupid conspiracy theorist. You never thought I’d be the winner.” He shrugged. “Well, here I am. I’m going to be rich and powerful and I’ll know everything.”

Lizzie closed her eyes. “I liked you, Grady. We all did.”

“Liar.” Grady’s voice was mild.

Finally, Will abandoned his efforts to save Carmen and got to his feet.

“I had plans for Carmen,” he said. And for the second time I heard true emotion in his voice – cold fury. “She was mine. You don’t mess with what’s mine. She was in my future.”

“Well, now you don’t have a future.” Grady looked at the monitors. “Mr Gold, I’ve done what you asked.” Sweat burst on to his upper lip. “Aren’t you going to come and get me?”

The monitor remained quiet.

“He’s still letting this play out,” Will said. “Aren’t you, Mr Gold? After all, there’s more than one psychopath in the room.” He offered his odd half-smile. Then he looked at me and Lizzie. “I’ve thought of a way we can get out of here.”

“What?” Grady held up his hands. “Now listen – I did what you asked.” He was still appealing to the monitors. “You offered a deal and I took it.”

Will was looking at the two of us. “Right now, Gold has Grady. But if he doesn’t have him…”

“Then we’ll be back where we were a minute ago,” Lizzie croaked. “Your hands around my neck. Don’t think I’ve forgotten!”

Will shook his head firmly. “No. If we all kill Grady together, then we all win. He has to take the three of us.”

“I’m not sure he has to do anything,” I muttered. I was exhausted.

Will focused on Lizzie. “If anyone deserves to die, it’s Grady. You know what he is now. See what he did to my Carmen? He’s just standing there, waiting for Gold to take him away and kill the rest of us. Are you OK with that?”

Grady was backing away now, edging to the corner of the room. “Mr Gold!”

“You think there’s an afterlife, Grady? You think you’ll find the answers you want there?” Will stalked him, kicking the bloody penknife into the far corner as he passed it.

Lizzie dragged herself to her feet, her hands curled into claws. “Do you still feel like a winner?”

I stared at my own bloody hands. If I didn’t join in, didn’t help them kill Grady, I’d be next. Will was right, there was only one way out. I looked at Carmen. She lay facing the wall, her back to the rest of us, as if in death, she chose not to see us.

Gold, however, was watching the spectacle avidly, his eyes sparkling.

“Mr Gold!” Grady squeaked.

Will reached out and grabbed the front of his shirt. There was a ripping sound as Grady twisted away.

Then another noise shattered the air – a high-pitched ding. We all jumped and I shook my arm to reveal Grandad’s watch. It was shuddering on my wrist as the alarm sounded.

“The estuary,” Lizzie said, with wonder in her voice. “The tide’s going out, the crossing is rising.” She grabbed Will’s arm. “If we can get out, we can go home.”

Will punched Grady as hard as he could in the forehead. Grady’s head smacked back, cracked against the wall and he slid to the floor.

I lurched to my feet and staggered to the knife lying on the floor. It was slick in my hands, wet with Carmen’s blood.

I picked it up.

Lizzie froze. “Ben, what are you doing?”

I staggered to the monitors and took the black wire in my fingers. The plastic surrounding it was almost tacky, organic.

“Worst case, it kills the lights and opens the door to the other teams,” I said tiredly. “We can tell them what Gold really wants – that he intends for most of us to die in that plane crash.”

“They’ll have to be on our side.” Lizzie’s fingers went to her hair, twisting.

“It could kill the power and trap us here for ever,” Will muttered.

I shrugged and placed the blade under the wire.

“Ben!” Lizzie cried out and I looked round. A yellowish gas was spreading into the room from the edges of the floor.

“Hurry, Ben!” Will pulled his T-shirt over his face and I saw Lizzie’s pale belly as she did the same thing.

The gas rose faster than I could have imagined and I took a deep breath, trying to hold it as it started to fill the air.

I began to saw.

The blade was slippery, the wire strong, and my hands shaking.

Lizzie and Will met in the centre of the room, standing back to back.

My eyes watered.

Will collapsed to his knees.

With a final heave of my shoulders, I jerked hard and felt the knife bite into the sheath. Then I yanked my arm backwards and sliced through.

Instantly the bright lights flooding the room went out.

I could no longer see Lizzie or Will – or the gas. What would happen if I took a tiny breath? Flashes of red light burst inside my eyes as my body fought for air, and then a blue glow. It took me a moment to realize that the blue was some kind of emergency lighting.

I squinted into the dimness and heard, as much as saw, the click and shush of an opening door. Immediately fresher air started to dissipate the gas being piped into the room.

The monitors flickered and revealed Gold’s face again.

Will was coughing. I could hear him over the hiss of the gas and realized he had fallen on his face. I pulled my T-shirt over my broken nose and stumbled across to him. I was running on empty; my adrenalin had gone; my body was on its last reserves. All I wanted to do was sleep. I found Will’s arm and hoisted him up with a grunt.

There was a thud, a yell and footsteps on the stairs. Will was right, cutting the wire had opened the main door. The other teams were on their way.

Then Lizzie’s face was next to mine. It seemed distorted – stretched out of all proportion, like a distended balloon. She was pointing frantically.

I turned to see her gesture at a second doorway, a rectangle that opened into darkness – one I hadn’t seen before.

“A secret door,” I said. “Secret door. Se-cret-door. See-crit—” The words tasted like insects scuttling across my tongue.

“It’s the gas,” Lizzie shouted. She caught my shoulder and shoved me towards the opening.

“Stop!” Gold ordered. “There’s nothing for you that way. If you leave, I’ll destroy you. I’ll ruin your families – everyone you’ve ever cared about.”

I showed him a middle finger and felt Will trying to regain his feet. “Come on, bro, we’re going home.”

I used the door frame to pull us into another corridor. The emergency lights turned everything blue, so that it was almost like swimming. Will coughed in my ear. Lizzie was ahead, holding on to the wall. The echoing corridor seemed endless, but we were definitely heading downhill; the clean air swept the gas from my lungs and I began to think more clearly.

Will took his own weight and I let him go. He looked back. “Can you hear them?”

“Yeah.”

We weren’t the only ones in the corridor.

I broke into a shambling run, pushing Lizzie to speed up. Behind us came an wailing howl: some jerk pretending to be a wolf. The sound was taken up by others and, despite myself, I trembled. Perhaps it was the gas, but it was all too easy to picture slavering beasts behind us, rather than kids our own age.

Not just kids. I shook my head. Psychopaths. More than one in each team.

Lizzie gave an exhausted sob, but I couldn’t help her; I could barely keep moving myself. It felt as if I was falling – my body was numb from the waist down, my feet only moving because it was the last command I’d given them. I wasn’t sure I even knew how to stop any more; only that if I did, I wouldn’t get up again.

Abruptly the corridor ended. Somehow, I’d ended up in front. When had I overtaken Lizzie? I stared stupidly at the door in front of me.

“It’s another door,” I said.

Will came up behind me, then Lizzie.

“No! It’s not fair.” Lizzie collapsed against the door with a wail … and fell forwards into the light.

“It opened.” I looked at Will. “It just … opened.”

Will nodded and we stepped out into rain – where had the sun gone?

The door shut behind us and I looked back. Then I blinked. The door had vanished; in its place, nothing but a crack in a rock wall.

I looked down. I was standing on soaking shingle. I lifted my head, then I started to laugh. We had emerged on the edge of a beach, surrounded by cliffs. In front of us, sharp, tooth-like rocks were ranged in a half-circle and, still caught on a stone spur, tangled in the shrinking pools, I could see Grady’s paracord belt.

“What is it?” Will frowned.

I could only point.

“You mean … we’re back where we started?” Lizzie rasped.

I sniggered, then laughed. My sides ached and I held them tight, but I couldn’t stop. I was hysterical. Raindrops pattered hard on my forehead and ran down my face – cooling, refreshing. Ahead of us, the crossing was rising, straight edges appearing in the sand. In the far distance, a splash of red – a phone box, civilization.

Lizzie dragged a hand through her short hair and her eyes were haunted. I saw with shame that silenced me that her throat was bruised. “We have to get back to the first checkpoint if we want to use Gold’s crossing. The tide isn’t all the way out either.”

She was right. Although patches of wet sand were dotting the distance, the water near us was still at least neck-high; the currents would be too dangerous if we tried to leave now. I nodded. “The only way off this beach was up that cliff, remember?” I swallowed. “I’m not sure I can climb it right now.”

“We don’t have a choice,” Will said.

Lizzie nodded. I looked behind me. The door had closed on Curtis’s howls, but he had to be right behind us.