'It's off the clacks!' he yelled. 'We've got Carcer cornered in New Hall! I've got to get down there now!'

'How exciting,' said Lord Vetinari, standing up suddenly. The call to the chase. But is it necessary for you to attend personally, your grace?' Vimes gave him a grey look. 'Yes,' he said. 'Because if I don't, y'see, some poor sod who's been trained by me to do the right thing is going to try to arrest the bugger.' He turned to Carrot. 'Captain, get on it right now! Clacks, pigeons, runners, whatever. I want everyone answering this shout, okay? But no one, I repeat, no one is to try to tackle him without a lot of backup! Understood? And get Swires airborne! Oh, damn 'What's wrong, sir?' said Carrot. 'This message is from Littlebottom. She sent it straight here. What's she doing there? She's Forensic. She's not street! She'll do it by the book!'

'Shouldn't she?' said Vetinari. 'No. Carcer needs an arrow in his leg just to get his attention. You shoot first-'

'-and ask questions later?' said Vetinari. Vimes paused at the door and said, There's nothing I want to ask him.' Vimes had to slow down for breath in Sator Square, and that was disgusting. A few years ago he'd've only really been getting into his stride by now! But the storm rolling over the plains was driving the heat before it, and it wouldn't do for the commander to turn up wheezing. As it was, even after pausing behind a street market stall for a few gulps of air, he doubted if he had enough wind left for a lengthy sentence. To his tremendous relief, an entirely unwounded Corporal Cheery Littlebottom was waiting by the University walls. She saluted. 'Reporting, sir,' she said. 'Mm,' murmured Vimes. 'I spotted a couple of trolls on traffic duty, sir,' said Cheery, 'so I've sent them round to the Water Bridge. Then Sergeant Detritus turned up and I told- I advised him to go into the University via main gate and get up high. Sergeant Colon and Nobby arrived and I sent them along to the Bridge of Size-'

'Why?' said Vimes. 'Because I doubt if he's really going to try going that way,' said Cheery, her face a very careful picture of innocence. Vimes had to stop himself from nodding. 'And then as more people come along I'm putting them around the perimeter. But I think he's gone up and he's staying high.'

'Why?'

'Because how's he going to fight his way out through a lot of wizards, sir? His best chance is to sneak around on the roofs and drop down somewhere quiet. There's a lot of hiding places and he can get all the way to Peach Pie Street without coming down.' Forensic, thought Vimes. Hah. And with any luck he doesn't know about Buggy. 'Well thought out,' he said. 'Thank you, sir. Would you mind standing a bit closer to this wall, sir?'

'What for?' Something shattered on the cobbles. Vimes was suddenly flat against the wall. 'He's got a crossbow, sir,' said Cheery. 'We think he stole it from Stronginthearm. But he's not very good with it.'

'Well done, corporal,' said Vimes weakly. 'Good job,' he glanced around the square behind him. The wind was whipping at the awnings of the market stalls and the traders, with occasional looks at the sky, were covering their wares. 'But we can't just let him hang around up there,' he went on. 'He'll start taking pot shots and he's bound to hit someone.'

'Why would he do that, sir?'

'Carcer doesn't need a reason,' said Vimes. 'He just needs an excuse.' A movement far above caught his eye, and he grinned. A large bird was gaining height over the city. The heron, mumbling complaints, fought for altitude in big, sweeping circles. The city whirled around Corporal Buggy Swires as he gripped even harder with his knees, and then he swung the bird downwind and it landed with a staggering run on the top of the Tower of Art, the highest building in the city. With a practised movement the gnome sliced through the string holding the portable semaphore in place, and leapt down after it into the compost of ivy leaves and old ravens' nests that carpeted the top of the tower. The heron watched him with round-eyed stupidity. Buggy had tamed it in the usual gnome way; you painted yourself green like a frog and hung out in the marshes, croaking, and then when a heron tried to eat you, you ran up its beak and nutted it. By the time it came round you'd blown the special oil - that had taken all day to make, and the stink of it had emptied the Watch House - up its nostrils and it took one look at you and thought you were its mum. A heron was useful. It could carry equipment. But Buggy preferred a sparrowhawk for traffic patrol. It was better for hovering. He slotted the portable semaphore arms on to the post he'd secretly installed weeks ago. Then he unshipped a tiny telescope from the heron's

saddlebags and strapped it on to the edge of the stone, looking almost straight down. Buggy liked moments like this. It was the only time that everyone else was smaller than him. 'Now . . . let's see what we can see,' he muttered. There were the University buildings. There was the clock tower of Old Tom, and the unmistakable bulk of Sergeant Detritus climbing among the nearby chimneys. The yellow light of the gathering storm glinted off the helmets of watchmen who were hurrying through the streets. And there, creeping along behind the parapet. . . 'Gotcha,' he said quietly, and reached for the handles of the semaphore. 'D . . . T . . . R . . . T . . . S space H...D...N...G space O . . . L space T . . . M,' said Cheery. Vimes nodded. Detritus was on the roof near the tower of Old Tom. And Detritus carried a siege crossbow that three men couldn't lift, and had converted it to fire a thick sheaf of arrows all at once. Mostly they shattered in the air because of the forces involved and the target was hit by an expanding cloud of burning splinters. Vimes had banned him from using it on people, but it was a damn good way of getting into buildings. It could open the front door and the back door at the same time. 'Tell him to fire a warning shot,' he said. If he hits Carcer with that thing we won't even find a corpse.' Though I'd quite like to find a corpse, he added to himself. 'Yes, sir.' Cheery pulled a couple of white-painted paddles out of her belt, sighted on the top of the tower, and sent a brief signal. There was an answering signal from the distant Buggy. 'D . . . T . . . R . . . T . . . S space W...R...N. ..G space S ... H ... T.' Cheery muttered to herself, as she waved the rest of the message. There was another answering dip from above. A moment later a red flare shot up from the top of the tower and exploded. It was an efficient way of getting everyone to pay attention. Then Vimes saw the message relayed. Around the University buildings, watchmen who'd also seen the order ducked into doorways. They knew about the bow. There were a few seconds for the troll to work out the spelling, a distant heavy thud, a sound like a swarm of hellish bees, and then a crash of tiles and masonry. Pieces of tile rained down into the square. An entire chimney, still with a wisp of smoke coming from it, smashed down a few yards from where Vimes was standing. Then there was the patter of dust and small bits of wood, and a gentle shower of pigeon feathers. Vimes shook some flakes of mortar off his helmet.'Yes, well, I think he's been warned,' he said. Half a weathercock landed next to the chimney.

Cheery blew some feathers off her telescope and sighted on the top of the tower again. 'Buggy says he's stopped moving, sir,' she reported. 'Really? You surprise me.' Vimes adjusted his belt. 'And now you can give me your crossbow. I'm going up.'

'Sir, you said no one was to try to arrest him! That's why I sent the signal to you!'

'That's right. I'm going to arrest him. Right now. While he's counting all his bits to check that he's still got 'em. Tell Detritus what I'm doing, 'cos I don't want to end up as 160lbs of cocktail delicacies. No, don't keep opening your mouth like that. By the time we've sorted out backup and armour and got everyone lined up he'll have dug in somewhere else.' The last words were delivered at a run. Vimes reached a door and darted inside. New Hall was student accommodation, but it was still only half past ten so most of them would be in bed. A few faces looked around doors as Vimes trotted along the corridor and reached the stairwell at the far end. That took him - walking now, and rather less sure of his future - to the top floor. Let's see, he'd been here before . . . yes, there was a door ajar, and a glimpse of mops and buckets suggested that this was a janitor's cupboard. With, at the far end, a ladder leading up to the roof. Vimes carefully cocked the crossbow. So Carcer had a Watch crossbow, too. They were good classic single-shot models, but they took a while to reload. If he fired at Vimes and missed, then that was the only shot he'd get. After that . . . you couldn't plan. Vimes climbed the ladder, and the song came back. 'They rise feet up, feet up, feet up . . .' he hissed under his breath. He stopped just below the edge of the open trapdoor on to the leads. Carcer wouldn't fall for the old 'helmet on stick' trick, not with only one shot available. He'd just have to risk it. Vimes thrust his head up, turned it quickly, ducked out of sight for a moment and then came through the opening in a rush. He rolled clumsily when he hit the leads, and rose into a crouch. There was no one else there. He was still alive. He breathed out. A sloping, gabled roof rose up beside him. Vimes crept along, wedged himself against a chimneystack peppered with splinters of wood, and glanced up at the tower. The sky above it was livid blue-black. Storms picked up a lot of personality as they rolled across the plains, and this one looked like a record breaker. But brilliant sunlight picked out the Tower of Art and, at the top, the tiny dots of Buggy's frantic signal. . . O . . . O . . . O

Officer In Trouble. A brother is hurtin'. Vimes spun around. There was no one creeping up on him. He eased himself around the chimneys and there, tucked between another couple of stacks and out of sight of everyone except Vimes and the celestial Buggy, was Carcer. He was taking aim. Vimes turned his head to spot the target. Fifty yards away, Carrot was picking his way across the top of the University's High Energy Magic building. The bloody fool was never any good at concealment. Oh, he ducked and crept, and against all logic that made him more noticeable. He didn't understand the art of thinking himself invisible. And there he was, furtively shlepping through the debris on the roof and looking as visible as a big duck in a small bathtub. And he'd come up without backup. The fool. . . Carcer was aiming carefully. The roof of the HEM was a maze of abandoned equipment and Carrot was moving along behind the raised platform that held the huge bronze spheres known throughout the city as The Wizards' Balls, which discharged surplus magic if - or more usually when - experiments in the hall below fouled up. Carrot, screened by all that, was not making such a good target. Vimes raised his crossbow. Thunder . . . rolled. It was the roll of a giant iron cube down the stairways of the gods, a crackling, thudding crash that tore the sky in half and shook the building. Carcer glanced up, and saw Vimes. 'Wotcha doin', mifter?' Buggy didn't budge from the telescope. A crowbar wouldn't have separated him at this point. 'Shut up, ye daft corbies!' he muttered. Both men below had fired, and both men had missed because they were trying to fire and dodge at the same time. Something hard prodded Buggy's shoulder. 'Wot's happ'nin', mifter?' said the insistent voice. He turned. There were a dozen bedraggled ravens behind him, looking like old men in ill-fitting black cloaks. They were Tower of Art birds. Hundreds of generations of living in a highly charged magical environment had raised the intelligence level of what had been bright creatures to begin with. But, although the ravens were intelligent, these ones weren't hugely clever. They just had a more persistent kind of stupidity, as

befitted birds for whom the exciting panorama of the city below was a kind of daytime TV. 'Push off!' shouted Buggy, and turned back to the telescope. There was Carcer, running, and Vimes running after him, and here came the hail... It turned the world white. It thudded around him and made his helmet ring. Hailstones as big as his head bounced on the stone and hit Buggy from underneath. Cursing, and shielding his face with his arms, and hammered all the time by shattering crystal balls, each one predicting a future of pain, he skidded and slid across the rolling ice. He reached an ivy-hung arch between two lesser turrets, where the heron had already taken refuge, and fell inside. Frozen shrapnel still ricocheted in and stung him, but at least he could see and breathe. A beak prodded him sharply in the back. 'Wot's happ'nin' now, mifter?' Carcer landed heavily on the arch between the student hall and the main buildings, almost lost his footing on the tiles, and hesitated. An arrow from a watchman below grazed his leg. Vimes dropped down behind him, just as the hail hit. Cursing and slipping, one man followed the other across the arch. Carcer reached a mass of ivy that led up on to the roof of the Library and scrambled up it, scattering ice below. Vimes grabbed the ivy just as Carcer disappeared on to the flat roof. He looked round at a crash behind him, and saw Carrot trying to make his way along the wall from the High Energy Magic building. The hail was forming a halo of ice fragments around him. 'Stay there!' Vimes bellowed. Carrot's reply was lost in the noise. Vimes waved his arms and then grabbed at the ivy as a foot slipped. 'Bloody stay there!' he yelled. 'That is an order! You'll go over!' He turned and started up the wet, cold vines. The wind dropped, and the last few hailstones bounced off the roof. Vimes stopped a few feet from the top of the ivy, worked his feet firmly into footholds in the ancient, knotted stems, and reached up for a decent hold. Then he thrust himself up, left hand ready, caught the boot that swung towards him and carried on rising, pushing Carcer off balance. The man sprawled backwards on the slippery hail, tried to get to his feet, and slipped again. Vimes tugged himself on to the roof, stepped forward, and found his legs skidding away beneath him. Both he and Carcer got up, tried to move, and fell over again. From a prone position the man landed a kick on Vimes's shoulder, sending both of them sliding away in opposite directions, and then turned over