'You can't think of anything civilized?'

'No. It's over to you, I'm afraid.'

'Hah! Hah! I bin waiting for this,' said Caleb, pushing forward. 'Bin practising every day, 'n I? With my big lump o' teak.'

'These are ninjas,' said Six Beneficent Winds proudly, as a couple of the men wandered towards the door and pulled it shut. 'The finest fighters in the world! Yield now!'

'That's interesting,' said Cohen. 'Here, you, in the black pyjamas . .. Just got out of bed, have you? Who's the best out of all of you?'

One of the men stared fixedly at Cohen and thrust out a hand at the nearest wall. It left a dent.

Then he nodded at the tax gatherer. 'What are these old fools you've brought us?'

'I think they're barbarian invaders,' said the tax-man.

'How'd you - How'd he know that?' said Boy Willie. 'We're wearin' itchy trousers and eatin' with forks and every thin'—'

The leading ninja sneered. 'Heroic eunuchs?' he said. 'Old men?'

'Who're you calling a eunuch?' Cohen demanded.

'Can I just show him what I've been practising with my lump o' teak?' said Caleb, hopping arthritically from one foot to the other.

The ninja eyed the slab of timber.

'You could not make a dent on that, old man,' he said.

'You watch,' said Caleb. He held out the wood at arm's length. Then he raised his other hand, grunting a little as it got past shoulder height.

'You watching this hand? You watching this hand?' he demanded.

'I am watching,' said the laugh.

'Good,' said Caleb. He kicked the man squarely in the groin and then, as he doubled up, hit him over the head with the teak.'

'Cos you should've been watchin' this foot.'

And that would have been all there was to it if there had only been one ninja. But there was a clatter of rice flails and an unsheathing of long, curved swords.

The Horde drew closer together. Hamish pushed back his rug to reveal their armoury, although the collection of notched blades looked positively homely compared with the shiny toys ranged against them.

'Teach, why don't you take Mr Taxman over to the corner out of harm's way?' said Ghenghiz.

This is madness!' said Six Beneficent Winds. 'They're the finest fighters in the world and you're just old men! Give in now and I'll see if I can get you a rebate!'

'Calm down, calm down,' said Mr Saveloy. 'No-one's going to get hurt. Metaphorically, at least.'

Ghenghiz Cohen waved his sword a few times.

'OK, you lads,' he said. 'Give us your best ninje.'

Six Beneficent Winds looked on in horror as the Horde squared up.

'But it will be terrible slaughter!' he said.

'I'm afraid so,' said Mr Saveloy. He fished in his pockets for a bag of peppermints.

'Who are these mad old men? What do they do?'

'Barbarian heroing, generally,' said Mr Saveloy, 'Rescuing princesses, robbing temples, fighting mon-sters, exploring ancient and terror-filled ruins... that sort of thing.'

'But they look old enough to be dead! Why do they do it?'

Saveloy shrugged. 'That's all they've ever done.'

A ninja somersaulted down the room, screaming, a sword in either hand; Cohen waited in an attitude rather similar to that of a baseball batter.

'I wonder,' said Mr Saveloy, 'if you have ever heard of the term "evolution"?'

The two met. The air blurred.

'Or "survival of the fittest"?' said Mr Saveloy.

The scream continued, but rather more urgently.

'I didn't even see his sword move!' whispered Six Beneficent Winds.

'Yes. People often don't,' said Mr Saveloy.

'But... they're so old!'

'Indeed,' said the teacher, raising his voice above the screams, 'and of course this is true. They are very old barbarian heroes.'

The taxman stared.

'Would you like a peppermint?' said Mr Saveloy, as Hamish's wheelchair thundered past in pursuit of a man with a broken sword and a pressing desire to stay alive. 'You may find it helps, if you are around the Horde for any length of time.'

The aroma from the proffered paper bag hit Six Beneficent Winds like a flamethrower.

'How can you smell anything after eating those?'

'You can't,' said Mr Saveloy happily.

The taxman continued to stare. The fighting was a fast and furious affair but, somehow, only on one side. The Horde fought like you'd expect old men to fight - slowly, and with care. All the activity was on the part of the ninjas, but no matter how well flung the throwing star or speedy the kick, the target was always, without any obvious effort, not there.

'Since we have this moment to chat,' said Mr Saveloy, as something with a lot of blades hit the wall just above the taxman's head, 'I wonder: could you tell me about the big hill just outside the city? It is quite a remarkable feature.'

'What?' said Six Beneficent Winds distractedly.

'The big hill.'

'You want to know about that? Now?'

'Geography is a little hobby of mine.'

Someone's ear hit Six Beneficent Winds on the ear.

'Er. What? We call it the Big Hill... Hey, look at what he's doing with his—'

'It seems remarkably regular. Is it a natural feature?'

'What? Eh? Oh... I don't know, they say it turned up thousands of years ago. During a terrible storm. When the first Emperor died. He... he's going to be killed! He's going to be killed! He's going to be - How did he do that?'

Six Beneficent Winds suddenly remembered, as a child, playing Shibo Yangcong-san with his grand-father. The old man always won. No matter how carefully he'd assembled his strategy, he'd find Grand-father would place a tile quite innocently right in the crucial place just before he could make his big move. The ancestor had spent his whole life playing shibo. The fight was just like that.

'Oh, my,' he said.

'That's right,' said Mr Saveloy. 'They've had a lifetime's experience of not dying. They've become very good at it.'

'But... why here? Why come here?'

'We're going to undertake a robbery,' said Mr Saveloy.

Six Beneficent Winds nodded sagely. The wealth of the Forbidden City was legendary. Probably even blood-sucking ghosts had heard of it.

'The Talking Vase of Emperor P'gi Su?' he said.

'No.'

'The Jade Head of Sung Ts'uit Li?'

'No. Wrong track entirely, I'm afraid.'

'Not the secret of how silk is made?'

'Good grief. Silkworms' bottoms. Everyone knows that. No. Something rather more precious than that.'

Despite himself, Six Beneficent Winds was impressed. Apart from anything else, only seven ninjas were still standing and Cohen was fencing with one of them while rolling a cigarette in the other hand.

And Mr Saveloy could see it dawning in the fat man's eyes.

The same thing had happened to him.

Cohen came into people's lives like a rogue planet into a peaceful solar system, and you felt yourself being dragged along simply because nothing like that would ever happen to you again.

He himself had been peacefully hunting for fossils during the school holidays when he had, more or less, stumbled into the camp of those particular fossils called the Horde. They'd been quite friendly, because he had neither weapons nor money. And they'd taken to him, because he knew things they didn't. And that had been it.

He'd decided there and then. It must have been something in the air. His past life had suddenly unrolled behind him and he couldn't remember a single day of it that had been any fun. And it had dawned on him that he could join the Horde or go back to school and, pretty soon, a limp handshake, a round of applause and his pension.

It was something about Cohen. Maybe it was what they called charisma. It overpowered even his normal smell of a goat that had just eaten curried asparagus. He did everything wrong. He cursed people and used what Mr Saveloy considered very offensive language to foreigners. He shouted terms that would have earned anyone else a free slit throat from a variety of interesting ethnic weapons - and he got away with it, partly because it was clear that there was no actual malice there but mainly because he was, well, Cohen, a sort of basic natural force on legs.