He stuck one leg over the sill and unhitched his line and grapnel. He hooked the gutter two floors up and slipped out of the window.

No assassin ever used the stairs.

In order to establish continuity with later events, this may be the time to point out that the greatest mathematician in the history of the Discworld was lying down and peacefully eating his supper.

It is interesting to note that, owing to this mathematician's particular species, what he was eating for his supper was his lunch.

Gongs around the Ankh-Morpork sprawl were announcing midnight when Teppic crept along the ornate parapet four storeys above Filigree Street, his heart pounding.

There was a figure outlined against the afterglow of the sunset. Teppic paused alongside a particularly repulsive gargoyle to consider his options.

Fairly solid classroom rumour said that if he inhumed his examiner before the test, that was an automatic pass. He slipped a Number Three throwing knife from its thigh sheath and hefted it thoughtfully. Of course, any attempt, any overt move which missed would attract immediate failure and loss of privileges2.

The silhouette was absolutely still. Teppic's eyes swivelled to the maze of chimneys, gargoyles, ventilator shafts, bridges and ladders that made up the rooftop scenery of the city.

Right, he thought. That's some sort of dummy. I'm supposed to attack it and that means he's watching me from somewhere else.

Will I be able to spot him? No.

On the other hand, maybe I'm meant to think it's a dummy. Unless he's thought of that as well . . .

He found himself drumming his fingers on the gargoyle, and hastily pulled himself together. What is the sensible course of action at this point?

A party of revellers staggered through a pool of light in the street far below.

Teppic sheathed the knife and stood up.

'Sir,' he said, 'I am here.'

A dry voice by his ear said, rather indistinctly, 'Very well.'

Teppic stared straight ahead. Mericet appeared in front of him, wiping grey dust off his bony face. He took a length of pipe out of his mouth and tossed it aside, then pulled a clipboard out of his coat. He was bundled up even in this heat. Mericet was the kind of person who could freeze in a volcano.

'Ah,' he said, his voice broadcasting disapproval, 'Mr. Teppic. Well, well.'

'A fine night, sir,' said Teppic. The examiner gave him a chilly look, suggesting that observations about the weather acquired an automatic black mark, and made a note on his clipboard.

'We'll take a few questions first,' he said.

'As you wish, sir.'

'What is the maximum permitted length of a throwing knife?' snapped Mericet.

Teppic closed his eyes. He'd spent the last week reading nothing but The Cordat; he could see the page now, floating tantalisingly just inside his eyelids — they never ask you lengths and weights, students had said knowingly, they expect you to bone up on the weights and lengths and throwing distances but they never— Naked terror hotwired his brain and kicked his memory into gear. The page sprang into focus.

'"Maximum length of a throwing knife may be ten finger widths, or twelve in wet weather»,' he recited. '"Throwing distance is-« 'Name three poisons acknowledged for administration by ear.' A breeze sprang up, but it did nothing to cool the air; it just shifted the heat about.

'Sir, wasp agaric, Achorion purple and Mustick, sir,' said Teppic promptly.

'Why not spime?' snapped Mericet, fast as a snake. Teppic's jaw dropped open. He floundered for a while, trying to avoid the gimlet gaze a few feet away from him.

'S-sir, spime isn't a poison, sir,' he managed. 'It is an extremely rare antidote to certain snake venoms, and is obtained-' He settled down a bit, more certain of himself: all those hours idly looking through the old dictionaries had paid off— 'is obtained from the liver of the inflatable mongoose, which-'

'What is the meaning of this sign?' said Mericet.

'— is found only in the…' Teppic's voice trailed off. He squinted down at the complex rune on the card in Mericet's hand, and then stared straight past the examiner's ear again.

'I haven't the faintest idea, sir,' he said. Out of the corner of his ear he thought he heard the faintest intake of breath, the tiniest seed of a satisfied grunt.

'But if it were the other way up, sir,' he went on, 'it would be thiefsign for «Noisy dogs in this house There was absolute silence for a moment. Then, right by his shoulder, the old assassin's voice said, 'Is the killing rope permitted to all categories?'

'Sir, the rules call for three questions, sir,' Teppic protested.

'Ah. And that is your answer, is it?'

'Sir, no, sir. It was an observation, sir. Sir, the answer you are looking for is that all categories may bear the killing rope, but only assassins of the third grade may use it as one of the three options, sir.'

'You are sure of that, are you?'

'Sir.'

'You wouldn't like to reconsider?' You could have used the examiner's voice to grease a wagon.

'Sir, no, sir.'

'Very well.' Teppic relaxed. The back of his tunic was sticking to him, chilly with sweat.

'Now, I want you to proceed at your own pace towards the Street of Book-keepers,' said Mericet evenly, 'obeying all signs and so forth. I will meet you in the room under the gong tower at the junction with Audit Alley. And — take this, if you please.'

He handed Teppic a small envelope.

Teppic handed over a receipt. Then Mericet stepped into the pool of shade beside a chimney pot, and disappeared.

So much for the ceremony.

Teppic took a few deep breaths and tipped the envelope's contents into his hand. It was a Guild bond for ten thousand Ankh— Morpork dollars, made out to 'Bearer'. It was an impressive document, surmounted with the Guild seal of the double-cross and the cloaked dagger.

Well, no going back now. He'd taken the money. Either he'd survive, in which case of course he'd traditionally donate the money to the Guild's widows and orphans fund, or it would be retrieved from his dead body. The bond looked a bit dog-eared, but he couldn't see any bloodstains on it.

He checked his knives, adjusted his swordbelt, glanced behind him, and set off at a gentle trot.

At least this was a bit of luck. The student lore said there were only half a dozen routes used during the test, and on summer nights they were alive with students tackling the roofs, towers, eaves and colls of the city. Edificing was a keen inter-house sport in its own right; it was one of the few things Teppic was sure he was good at — he'd been captain of the team that beat Scorpion House in the Wallgame finals. And this was one of the easier courses.

He dropped lightly over the edge of the roof, landed on a ridge, ran easily across the sleeping building, jumped a narrow gap on to the tiled roof of the Young Men's Reformed-Cultists-of— the-Ichor-God-Bel-Shamharoth Association gym, jogged gently over the grey slope, swarmed up a twelve foot wall without slowing down, and vaulted on to the wide flat roof of the Temple of Blind Io.

A full, orange moon hung on the horizon. There was a real breeze up here, not much, but as refreshing as a cold shower after the stifling heat of the streets. He speeded up, enjoying the coolness on his face, and leapt accurately off the end of the roof on to the narrow plank bridge that led across Tinlid Alley.

And which someone, in defiance of all probability, had removed.

At times like this one's past life flashes before one's eyes. . .

His aunt had wept, rather theatrically, Teppic had thought, since the old lady was as tough as a hippo's instep. His father had looked stern and dignified, whenever he could remember to, and tried to keep his mind free of beguiling images of cliffs and fish. The servants had been lined up along the hall from the foot of the main stairway, handmaidens on one side, eunuchs and butlers on the other. The women bobbed a curtsey as he walked by, creating a rather nice sine wave effect which the greatest mathematician on the Disc, had he not at this moment been occupied by being hit with a stick and shouted at by a small man wearing what appeared to be a nightshirt, might well have appreciated.