"Welcome back, my two little bunny rabbits," Surge said. "Nice warm afternoon, was it? Lovely choccy biscuits? Nursey made you all better? Well I have another special treat for you two love birds. Take off your boots and everything but your underwear, then go outside and, in the unlikely event you make it through the night, I'll let you come back in the morning. Remember, it's nice and warm in the main building if you want to quit." Ash and Serena stripped off and stepped into the dark.

"Merry Christmas," Surge shouted after them.

The door shut, closing off the last tiny arc of light. The wind was bitter. Frost burned their feet. Serena was only a few metres from Ash, but he could barely see her. Ash heard her sob.

"I'm sorry, Serena," Ash said. "This is all my fault." Serena didn't answer.

"Please talk to me, Serena. I know I was stupid. Seeing everyone sitting in the warm and it being Christmas made me crazy. You know?" Serena started crying quite noisily. Ash gently touched her shoulder. She backed off.

"Don't touch me, Ash." This was the first thing Serena had said to Ash since the fight.

"We can get through this together," Ash said. "I'm so sorry. You want me to beg? I'll go down on the ground and kiss your feet if you just start talking to me.

"Ash," Serena sobbed, "we're done for. You can say you're sorry a thousand times, but you've still got us both thrown out."

"We can get through this, Serena. Find somewhere warm and go to sleep." Serena laughed a little.

"Find somewhere warm! Ash, there is nowhere warm! There's a big muddy field and an assault course. Nothing else. It's already close to freezing. An hour out here and we'll start getting frostbite in our toes and fingers. It's fourteen hours until morning. If we fall asleep we'll die of cold."

"You don't deserve this, Serena. I'll bang on the door and ask to speak to Large. I'll say it's all my fault and that I'll quit if he lets you back inside."

"He won't bargain with you, Ash. He'll laugh in your face."

"We could start a fire," Ash said.

"It's raining. It's pitch dark. We'd need something dry to start the fire and somewhere out of the wind to start it. Any suggestions?"

"The bridge over the lake on the assault course," Ash said. "There's a gap under there before the water starts. We could put branches and stuff along the sides to keep out the wind."

"I suppose," Serena said. "We've got to try. There might be stuff in the rubbish."

"What?"

"There are two rubbish bins at the back of the building," Serena said. "We could go through them. There might be stuff inside we could use."

Serena led Ash to the back of the training building. They each pulled the lid off a bin. Both were full of rubbish tied up in bags.

"Reeks," Ash said.

"I don't care what it smells like," Serena said. "Here's what I'm thinking. We take the bins with all the stuff in to the bridge. Then we go through all the bags. Hopefully there's something to start a fire with. The bags will help us keep warm if we wear them."

It was hard finding the bridge in the moonlight. It was too dark to make out any more than the outline of the ground. There was a risk of hitting something sharp with every step. Ash and Serena took a bin each. They weighed a ton. Ash tried rolling his instead of carrying it, but the bin kept jamming in the mud. Serena was having an even tougher time because her hand was bandaged. They walked the path at the side of the assault course. Ash's feet were numb already. He thought about the gruesome photos of black frostbitten toes in the training manual and shuddered.

The wooden bridge spanned twenty metres over the river in the middle of the assault course, and was about two metres wide. When they reached it, Serena started untying and rummaging around inside the stinking rubbish bags. Ash clambered into the low space under the bridge.

"It's pretty dry under here," Ash said. "It's concrete, no mud."

"OK," Serena said. "I'm trying to get stuff to start a fire."

Ash ran back and forth, stripping off branches and wedging them against the side of the bridge. Serena dunked her hand in a bag and hit a mix of food slops and muddy rags used for boot cleaning. She sniffed her hand and couldn't believe she was touching all this nasty stuff. She threw anything that was dry and would burn into an empty bin.

Serena tore the bags up, covered her feet in the boot-cleaning rags and then wrapped them with plastic. She tore holes in bin bags to make a plastic smock and skirt for herself and Ash. They looked like muddy scarecrows, but the important thing was it kept out the cold. Ash finished turning the bridge into a shelter and they clambered under, rubbing their hands together.

"Here," Serena said. She handed Ash two small boxes. It was too dark to see what they were. Ash felt the familiar shape of a straw on the side of a carton.

"Breakfast," Ash said. "This was in the rubbish?"

"God must be on our side," Serena said. "Six cartons of orange juice, six mini packets of cereal, all unopened. Large must have thrown them out this morning when he didn't give us breakfast."

Ash punched the straw into the orange juice carton and sucked the contents in two long gulps. Then he ripped open the cereal and scoffed dry flakes.

"We've got clothes, food and shelter," Ash said. "We should last until morning."

"Maybe," Serena said. "I'd be happier if I could get the fire going."

"There's tons of stuff there that will burn," Ash said.

"But the only way I know to start a fire is with two dry pieces of timber. We've got zero."

They sat there for a few minutes, huddled close, jiggling arms and legs to keep warm.

"I think I know a way to start a fire," Ash said. "You know the security cameras all over the assault course?"

"What about them?" Ash asked.

"They must be powered by electricity."

"So what?"

"So if we find one and pull the power cord out the back then we can use it to make a spark."

"It's pitch dark," Serena said.

"I know roughly where a few of the cameras are."

"Ash, you're talking about messing with electricity. You could end up getting killed." Ash stood up. "Where are you going?"

"Have faith, Serena. I'm going to start a fire."

"You're a total idiot, Ash. You'll get zapped."

Ash clambered out of the shelter. The foot coverings Serena made kept his feet warm but slid everywhere. He found the bin Serena had filled with flammable stuff. He tucked bits of tissue and cardboard inside his plastic suit, then grabbed a dustbin lid and started his search. Ash found a camera only a few metres from the shelter. The tiny red lamp below the lens made it easier to spot the cameras in the dark than in daylight.

Ash felt behind the camera and tugged the wires out of the back. One looked like the picture output, so he threw it away. The other wire had a two-pronged rubber plug on the end. Ash figured this was the power supply. He twisted the plug until it snapped off, leaving two bare wires at the end of the lead.

It had seemed a good idea in theory. But now he was on the spot, with his little store of fuel standing on the dustbin lid, water all around and a live electric cable in his hand, Ash's confidence plummeted.

He crouched over the bin lid. He split the cable, pulling the two bare ends of wire further apart, then lined them up over a piece of tissue. He slowly moved the two ends closer together. A blue spark lit up Ash's face. The corner of the tissue ignited. A couple of embers flew off and the fire snuffed out. Ash's heart stopped. He doubted he'd get another chance because the spark had probably fused the circuit. Then a second burst of flame rose from the centre of the tissue. Ash dipped a scrap of cardboard in the flame. The fire caught hold.

He had to move back to the bridge before the fuel burned out. His feet slid everywhere and the wind was doing its best to kill the flames.

"Serena," Ash shouted. "Get some of the fuel." Serena dashed out and put more bits of card on the fire. The metal lid was getting hot in Ash's hands and the last part of the journey was trickiest, down the muddy river bank and into the shelter. Serena helped keep the lid steady. Ash pushed the lid into the shelter, careful not to set light to the branches lining the sides. Serena got the rest of the fuel and they cuddled up to each other as the shelter filled with flickering orange light. The smoke made their eyes sting, but all they cared about was being warm. Serena rested her head on Ash's arm.

"I still can't believe you stomped my hand," Serena said, looking at her bandage. "I thought we were a good team."

"I know sorry doesn't make it all better, but I really am Sere. If there's anything I can do to make it up, I will. Just name it."

"You know what," Serena said. "I'll forgive you now. But after training finishes I'll fight you in the dojo. I'll beat you until you scream for mercy. Then I'll beat you some more. And why did you call me Sere?" She asked with a slight blush.

"Deal," Ash said, hoping she was joking for the first part. "It's what I deserve for getting us into this mess. And I think it's a cute nickname..." he confessed while starting ahead, as Serena snuggled into his chest.

Marshal stuck his head inside the shelter. It was starting to get light. The fire was burned out. Ash and Serena were asleep with their arms around each other.

"Wake up," Marshal said.

Ash and Serena rustled to life in their plastic suits. Serena had said it was best not to go to sleep; better to stay alert and not get frostbite. But the shelter was warm and they'd both drifted off.

"I love you two with all my heart," Marshal said. Marshal reached into his trouser pocket and pulled out a couple of bars of Fruit and Nut. Ash couldn't understand why Marshal was being nice to them.

"I am so impressed with the way you two got through this. Lt Surge was convinced you would quit. He couldn't find you. All the video cameras have stopped working for some reason."

"What time is it?" Serena asked, cheeks stuffed with chocolate like a chipmunk.

"Six-thirty. You two better run back to the main building and get dressed. Lt Surge is going to be furious when he sees you."

"Doesn't he like us?" Ash asked. "I mean, I know he hates everyone, but why is he so keen to get rid of us?"

"You don't understand," Marshal said. "We had a bet. Fifty pounds that Lt Surge could make a trainee quit on Christmas Day. He thought making Brendan watch his brother eat Christmas dinner would work, but Drew told him to stick it out. Then you two started fighting, which gave him the excuse to punish you. He was sure he'd broken you. I can't wait to see the look on his face."

"After this he's gonna make our lives even more miserable," Serena sighed.