Exclusive short story by Anthony Horowitz - only in The Mail on Sunday

They don't receive phone calls in the middle of the night and disappear at the drop of a hat. And how many of them are proficient in Thai boxing and karate; speak three languages and keep themselves in perfect physical shape?

Ian Rider was a secret agent; a spy. From the day he left Cambridge University, he had worked for the Special Operations division of MI6.

Just about everything he told me was a lie, but I believed him because, as an orphan, I had no parents and had lived with him all my life. And, I suppose, because when you're 13 years old you believe what adults say.

But there was one occasion when I came very close to realising the truth. It happened one Christmas, at the ski resort of Gunpoint, Colorado. Although I didn't know it at the time, this was going to be the last Christmas we would spend together.

By the following spring, Ian would have been killed on a mission in Cornwall, investigating the Stormbreaker computers being manufactured there. That was just a couple of months after my 14th birthday, when my life span out of control and I was eventually to become a spy myself.

Gunpoint had been named after the man who first settled there, a gold prospector called Jeremiah Gun. It was about 50 miles north of Aspen, and if you've ever skied in America you'll know the set-up.

There was a central village with gas fires burning late into the night, mulled wine and toasted marshmallows, and shops with prices as high as the mountains around them.

We'd booked into a hotel, the Granary, which was on the edge of the village, about a five-minute walk to the main ski lift. The two of us shared a suite of rooms on the second floor. We each had our own bedroom, opening on to a shared living space with a balcony that ran round the side of the hotel.

The Granary was one of those brand-new places designed to look 100 years old, with big stone fireplaces, woven rugs and moose heads on the walls. I hoped they were fake, but they probably weren't.

For the first couple of days we were on our own. The snow was excellent. There had been a heavy fall just before we arrived, but at the same time the weather was unusually warm, so we were talking powder and lifts with no queues. Soon we were racing each other down the dizzyingly steep runs high up over Gunpoint itself.

It was on the third day that things changed. It began with two new arrivals who moved into the room next door: a father and his daughter who was just a couple of years older than me. Her name was Sahara.

Her dad lived and worked in Washington DC. She told me he was 'something in government', and I guessed she was being purposely vague. Her mother was a lawyer in New York. The two of them were divorced and Sahara had to share Christmases between them.

She was very pretty, with long black hair and blue eyes, only an inch taller than me despite the age gap. She'd been skiing all her life, and she was fearless. Unlike me, she had her own boots and skis. At the time my feet were growing too fast so, as usual, I'd had to rent.

Sahara Sands. Her father was Cameron Sands, with silver hair, silver glasses and a laptop computer that hardly seemed to leave his side. He spent every afternoon in his room, working. Sahara didn't seem to mind. She was used to it, and anyway, now she had Ian and me.

SUSPICIOUS MINDS

Two more people arrived on the same day as Sahara. They were sharing a smaller room across the corridor. I noticed them pretty quickly because they rarely seemed to be far away, although they never spoke to us.

They were both men in their late 20s, smartly dressed and very fit. They could have graduated from the same college.

One night in the hotel lounge I suggested they might be gay and Ian laughed. I' don't think so, Alex. Try again.' I thought for a moment. 'Are they bodyguards?'

'Better. At a guess, I'd say they're American Secret Service.'

I blinked. 'How do you know?'

'Well, they're both carrying guns.'

'Under their jackets?'

Ian shook his head. 'You could never draw a gun out of a ski jacket in time. They've got ankle holsters. Take a look the next time you see them.'

He looked at me over his brandy. 'You have to notice these things, Alex. Whenever you meet someone, you have to check them out... all the details. People tell a story the moment they walk into a room. You can read them.'

He was always saying stuff like that to me. I used to think he was just passing the time. It was only much later I realised he'd been preparing me. Just like the skiing and the scuba lessons. He was quietly following a plan that had begun almost the day I was born.

'Are they here with Cameron Sands?' I asked.

'What do you think?'

I nodded. 'They are always hanging around. And Sahara says her dad works in government.'

'Then maybe he needs protection.' Ian smiled. 'Let's see if you can find out their names by the end of the week,'he said. 'And the make of their guns.'

But the next day I had forgotten the conversation. It had snowed again. There must have been 10 inches on the ground, and it was bulging out over the roofs of the hotel like over-stuffed duvets.

Sahara and I switched to snowboards and spent about five hours on the chutes, bomb drops and powder stashes at the bowl area high up over Bear Creek.

I never guessed that just five months later I'd be using the same skills to avoid being killed by half a dozen thugs on snowmobiles, racing down the side of Point Blanc in southern France.

By half past three, with the sun already dipping behind the mountains, we decided to call it a day. We were both bruised, exhausted and soaked with sweat and melted snow. Sahara went off to meet her dad for a hot chocolate. I went back to the Granary on my own.

I had just dropped the board off at the rental shop and was slouching into the reception area when I saw my uncle, sitting on the corner of a sofa. I was about to call out to him - but then I stopped. I knew at once that something was wrong.

It's not easy to explain, but he had never looked like this before. He was completely silent and tense in a way that was almost animal. Ian had dark brown eyes, like me, but right now they were cold and colourless.

He hadn't noticed me come in: his attention was focused on the reception desk and a man who was checking into the hotel.

MYSTERY MAN

'People tell a story,' Ian had said. 'You can read them.' Looking at the man at the reception desk, I tried to do just that.

He was wearing a black rollneck jersey with dark trousers and a gold Rolex watch, heavy on his wrist.

He had blond hair; an intense yellow and cut short. It almost looked painted on. I would have said he was 30 years old, with a pock-marked face and a lazy smile. I could hear him talking to the receptionist. He had a Bronx accent.

So much for Chapter One. What else could I read in him? His skin was unusually pale. In fact it was almost white, as if he had spent half his life indoors. He worked out; I could see the muscles bulging under his sleeves.

And he had very bad teeth. That was strange. Americans wealthy enough to stay in a hotel like this would have taken more care of their dental work.

'You're on the fourth floor, Mr da Silva,' the receptionist said. 'Enjoy your stay.' The man had brought a cheap suitcase with him. That was also unusual in the land of Gucci and Louis Vuitton. He picked it up and disappeared into the lift.

I walked further into the reception area and Ian saw me. He knew I had been watching him. 'Is everything OK?' I asked.

'Yes.'

'Who was that?'

'The man who just checked in? I don't know.' Ian shook his head as if trying to dismiss the whole thing. 'I thought I knew him from somewhere. How was Bear Creek?'

He obviously didn't want to talk about it, so I went up to my room, showered and got ready for dinner.

As I made my way back downstairs, I noticed one of the Secret Service men coming out of their room. He walked off down the corridor without saying anything to me. Sahara and her father weren't around.

We ate. We talked. Ian ordered half a bottle of wine for himself and a Coke for me. At around half past ten I found myself yawning. Ian suggested I go up and watch TV.

'What about you?' I asked.

'Oh...I might get a breath of air. I'll follow you up later.'

I left him and went back to the room - and discovered I didn't have the electronic card that would open the door. I must have left it inside when I was getting changed.

I went back to the dining room. Ian was no longer there. Remembering what he had said, I followed him outside.

And there he was. I will never forget what I saw that night.

There was a courtyard round the side of the hotel, covered with snow, a frozen fountain in the middle. It was surrounded by walls on three sides, with the hotel roofs - also snow-covered -slanting steeply down. The whole area was lit by a full moon like a prison searchlight.

Ian Rider and the man who called himself Da Silva were locked together, standing like some bizarre statue in the middle of the courtyard. They were fighting for control of a single gun, clasped in their hands, high above their heads.

I could see the strain on their faces. But what made the scene even more surreal was that neither of them was making a sound. In fact they were barely moving. Both were focused on the gun. Whichever brought it down would be able to use it on the other.

I called out. It was a stupid thing to do. I could have got my uncle killed. Both men turned to look at me, but it was Ian who took advantage of the interruption.

He let go of the gun and slammed his elbow into Da Silva's stomach, then bent his arm up, the side of his hand scything the other man's wrist. I had already been learning karate for six years and recognised the perfectly executed sideways block.

The gun flew out of the man's hand, slid across the snow and came to rest in front of the fountain.

'Go back, Alex!' my uncle shouted.

It took him less than two seconds but it was enough to lose him the advantage. Da Silva lashed out, the heel of his hand pounding into Ian's chest, winding him.

A moment later the blond man wheeled round in a vicious roundhouse kick. My uncle tried to avoid it, but the snow, the slippery surface, didn't help. He was thrown off his feet and went crashing down.

Da Silva stopped and caught his breath. His mouth was twisted in an ugly sneer, his teeth grey in the moonlight. He knew the fight was over. He had won.

That was when I acted. I dived forward, throwing myself on to my stomach and sliding across the ice. My momentum carried me as far as the gun. I snatched it up, noticing for the first time that it was fitted with a silencer. I had never held a handgun before. It was much heavier than I had expected. Da Silva stared at me.

'No!' My uncle uttered the single word quietly. It didn't matter what the circumstances were. He didn't want me to kill a man.

SNOWED UNDER

I couldn't do that. I knew it, even as I lifted the gun and pulled the trigger. I emptied the gun - all seven bullets - but not at da Silva. I shot into the air above him, over his head. I felt the gun jerking in my hand. The recoil hurt my wrist. But then it was over. All the bullets had been fired.

Da Silva reached behind him and took out a second gun. My uncle was still on the ground; there was nothing he could do. I lay where I was, my breath coming out in white clouds. Da Silva raised his gun. I could see him deciding which one of us he was going to kill first.

And then there was a gentle rumble and a ton of snow slid off the roof directly above him. I had cut a dotted line with the bullets and - as I had hoped - the weight of the snow had done the rest.

Da Silva just had time to look up before the avalanche hit him. I think he opened his mouth -to swear or scream - but it was too late. The snow made almost no sound, just a soft thwump as it hit. In a second, he had gone. Buried under a huge white curtain.

My uncle got to his feet. I did the same. The two of us looked at each other. 'Do you think we should dig him up?' I asked.

He shook his head. 'No. Let's leave him to chill out.'

There were so many things I wanted to know when we finally got back to our room. 'Who was he? Why did he have a gun? Why were you fighting him?'

Ian had phoned the police. They were already on the way, he told me. He would talk to them when they arrived. The gun he and Da Silva had been fighting over was beside him. I could still feel the weight of it in my hand. My wrist was aching from the recoil; I had never fired a handgun before.

'Forget about it, Alex,' he said. 'I recognised Da Silva from a news story. He's a wanted criminal. Bank fraud...'

'Bank fraud?' I could hardly believe it.

'I met him outside quite by chance. I challenged him - which was pretty stupid of me. He pulled out the gun...and the rest you saw.' Ian smiled. 'I expect he'll have frozen solid by now. At least he won't be needing a morgue.'

If I'd thought a little more, I'd have realised none of this added up. When I had come upon the two men, they were fighting for control of a single gun.

They had dropped it - and then Da Silva had produced a second gun of his own. So logic should have told me the first gun belonged to my uncle.

But why would he have brought a gun with him on a skiing holiday? How could he even have got it through airport security? It was such an unlikely thought - Ian carrying a firearm - that I accepted his story because there was no alternative.

Anyway, I was exhausted. It had been a long day and I was glad to crawl into bed. The next morning Ian told me he wouldn't be coming skiing.

Apparently he'd spoken to the police when they finally arrived, and they wanted him to go to the precinct and tell them as much as he could about Da Silva and the fight outside the hotel. The bad news was, Da Silva had got away.

'He must have burrowed out,' Ian said over breakfast; boiled eggs and grilled bacon. He never ate anything fried.

'Do you think he'll come back?' I asked. Ian shook his head. 'I doubt it. He knows I recognised him and he's probably out of Colorado by now. He won't want to hang around.'

'How long do you think you'll be?'

'A few hours. Don't let this spoil the holiday, Alex. Put it out of your mind. You can ski with Sahara today. She'll be glad to have you on your own.'

SLIPPERY SLOPE

But Sahara wasn't in her room. When I knocked on her door, it was opened by her father, Cameron.

'I'm sorry, Alex,' he said. 'You're just too late. She left a few minutes ago. But she'll probably call in later. I can ask her to meet you.'

'Thanks,' I said. 'I'll be up at Bear Creek.'

He nodded and closed the door, and as he did so I looked over his shoulder and saw he wasn't alone. The two young men were with him; one sitting on the sofa, the other standing by the window. The Secret Service men.

I could see his desk too. There, as always, was the laptop, surrounded by a pile of papers. If this was a holiday, I wondered what Cameron Sands did when he was at work.

I went downstairs to the boot room and a few minutes later I was clumping out to the ski lift with my skis over my shoulder. I wondered if Sahara would be able to find me. There were quite a few people around, and the thing about skiers is they all look more or less the same.

On the other hand, I was wearing a bright green jacket; a North Face Freethinker. She'd already joked about the colour and I was sure she'd recognise it a mile away.

But I saw her before she saw me. The nearest lift to the hotel was a gondola, taking 20 people at a time up to an area called Black Ridge, about 1,000 metres higher up. Sahara was at the front of the queue, standing between two men.

I knew right away they weren't ski instructors. They were too close to her, sandwiching her between them as if they didn't want to let her slip away.

One of them was round-faced and white. The other looked Korean or Japanese. Neither were smiling. They were big men: even with the ski suits I got a sense of over-worked muscle. Sahara was scared, I saw that too. And a moment later I saw why.

A third man had gone ahead of them and was waiting inside the gondola. I only glimpsed his face behind the glass but I recognised it instantly. It was Da Silva. His hood was up and he was wearing sunglasses, but his pale skin and ugly teeth were unmistakable. He was waiting while the other men joined him with the girl.

I started towards them, but I was already too late. Sahara was inside the gondola. The doors slid shut and the whole thing jerked forward, rising up over the snow. Sahara caught sight of me just as she was swept away. Her eyes widened and she jerked her head in the direction of the hotel. The message was obvious. Get help!

Sahara was being kidnapped in broad daylight. It was crazy, but there could be no doubt about it.

I turned and began to run...