Guards! Guards!

Vimes gave him a sidelong look. 'Er,' he said. 'Yeah. Yes. That's right.'

On the roof of her house on the hill, Lady Ramkin adjusted a rather inadequate folding chair on the roof, arranged the telescope, coffee flask and sandwiches on the parapet in front of her, and settled down to wait. She had a notebook on her knee.

Half an hour went by. Hails of arrows greeted a passing cloud, several unfortunate bats, and the rising moon.

'Bugger this for a game of soldiers,' said Nobby, eventually. 'It's been scared off.'

Sgt Colon lowered his pike. 'Looks like it,' he conceded.

'And it's getting chilly up here,' said Carrot. He politely nudged Captain Vimes, who was slumped against the chimney, staring moodily into space.

'Maybe we ought to be getting down, sir?' he said. 'Lots of people are.'

'Hmm?' said Vimes, without moving his head.

'Could be coming on to rain, too,' said Carrot.

Vimes said nothing. For some minutes he had been watching the Tower of Art, which was the centre of Unseen University and reputedly the oldest building hi the city. It was certainly the tallest. Time, weather and indifferent repairs had given it a gnarled appearance, like a tree that has seen too many thunderstorms.

He was trying to remember its shape. As in the case with many things that are totally familiar, he hadn't really looked at it for years. Now he was trying to convince himself that the forest of little turrets and crenellations at its top looked just the same tonight as they had done yesterday.

It was giving him some difficulty.

Without taking his eyes off it, he grabbed Sgt Colon's shoulder and gently pointed him in the right direction.

He said, 'Can you see anything odd about the top of the tower?'

Colon stared up for a while, and then laughed nervously. 'Well, it looks like there's a dragon sitting on it, doesn't it?'

'Yes. That's what I thought.'

'Only, only, only when you sort of look properly, you can see it's just made up out of shadows and clumps of ivy and that. I mean, if you half-close one eye, it looks like two old women and a wheelbarrow.'

Vimes tried this. 'Nope,' he said. 'It still looks like a dragon. A huge one. Sort of hunched up, and looking down. Look, you can see its wings folded up.'

'Beg pardon, sir. That's just a broken turret giving the effect.'

They watched it for a while.

Then Vimes said, 'Tell me, Sergeant — I ask in a spirit of pure inquiry — what do you think 's causing the effect of a pair of huge wings unfurling?'

Colon swallowed.

'I think that's caused by a pair of huge wings, sir,' he said.

'Spot on, Sergeant.'

The dragon dropped. It wasn't a swoop. It simply kicked away from the top of the tower and half-fell, half-flew straight downwards, disappearing from view behind the University buildings.

Vimes caught himself listening for the thump.

And then the dragon was in view again, moving like an arrow, moving like a shooting star, moving like something that has somehow turned a thirty-two feet per second plummet into an unstoppable upward swoop. It glided over the rooftops at little more than head height, all the more horrible because of the sound. It was as though the air was slowly and carefully being torn in half.