'I mean the symbols. These symbols, just here.'
'Dunno, captain. They do look familiar, though. Sort of . . . like alchemists' writing?'
'Oh, no!' Vimes put his hands over his eyes. 'Not the bloody alchemists! Oh, no! Not that bloody gang of mad firework merchants! I can take the Assassins, but not those idiots! No! Please! What time is it?'
Carrot glanced at the hourglass on his belt. 'About half past eleven, captain.'
'Then I'm off to bed. Those clowns can wait until tomorrow. You could make me a happy man by telling me that this paper belonged to Hammerhock.'
'Doubt it, sir.'
'Me too. Come on. Let's go out through the back door.'
Carrot squeezed through.
'Mind your head, sir.'
Vimes, almost on his knees, stopped and stared at the doorframe.
'Well, corporal,' he said eventually, 'we know it wasn't a troll that did it, don't we? Two reasons. One, a troll couldn't get through this door, it's dwarf sized.'
'What's the other reason, sir?'
Vimes carefully pulled something off a splinter on the low door lintel.
'The other reason, Carrot, is that trolls don't have hair.'
The couple of strands that had been caught in the grain of the beam were red and long. Someone had left them there inadvertently. Someone tall. Taller than a dwarf, anyway.
Vimes peered at them. They looked more like threads than hair. Fine red threads. Oh, well. A clue was a clue.
He carefully folded them up in a scrap of paper borrowed from Carrot's notebook, and handed them to the corporal.
'Here. Keep this safe.'
They crawled out into the night. There was a narrow, plank walkway attached to the walls, and beyond that was the river.
Vimes straightened up carefully.
'I don't like this, Carrot,' he said. 'There's something bad underneath all this.'
Carrot looked down.
'I mean, there are hidden things happening,' said Vimes, patiently.
'Yes, sir.'
'Let's get back to the Yard.'
They proceeded to the Brass Bridge, quite slowly, because Carrot cheerfully acknowledged everyone they met. Hard-edged ruffians, whose normal response to a remark from a Watchman would be genteelly paraphrased by a string of symbols generally found on the top row of a typewriter's keyboard, would actually smile awkwardly and mumble something harmless in response to his hearty, 'Good evening, Masher! Mind how you go!'
Vimes stopped halfway across the bridge to light his cigar, striking a match on one of the ornamental hippos. Then he looked down into the turbid waters.
'Carrot?'
'Yes, captain?'
'Do you think there's such a thing as a criminal mind?'