Thud!

some dwarfs to try anything. Sam hoped the boy would be impressed; the most other kids could hope for was angels.
    Vimes had commandeered the canteen, because it had a big enough table. He’d spread out a map of the city. A lot of the rest of the planking was occupied by pages from the Koom Valley Codex .
    This wasn’t a game, this was a puzzle. A sort of, yes, jigsaw puzzle. And he ought to be able to do it, he reasoned, because he already had nearly all the corners.
    “Ettercap Street, Money Trap Lane, Crybaby Alley, Scuttle-butt Court, the Jeebies, Pellicool Steps,” he said. “Tunnels everywhere! They were lucky to find it after only three or four. Mr. Rascal must have had lodgings in half the streets in the area. Including Empirical Crescent!”
    “But hwhy?” said Sir Reynold Stitched. “I mean, hwhy dig tunnels everyhwhere?”
    “Tell him, Carrot,” said Vimes, drawing a line across the city.
    Carrot cleared his throat. “Because they were dwarfs, sir, and deep-downers at that,” he said. “It wouldn’t occur to them not to dig. And mostly it’d be just a matter of clearing out buried rooms, in any case. That’s a stroll, to a dwarf. And they were laying rails, so they could take the spoil out anywhere they wanted.”
    “Yes, but sureleah—” Sir Reynold began.
    “They were listening out for something talking at the bottom of an old well,” said Vimes, still bending over the map. “What chance that’d still be visible? And people can get a bit iffy when a bunch of dwarfs turn up and start digging holes in the garden.”
    “It’d be very slow, sureleah?”
    “Well, yes, sir. But it would be in the dark, under their control, and secret,” said Carrot. “They could go anywhere they wanted. They could zigzag around if they weren’t certain, they could home in with their listening tube, and they’d never have to speak to a human or see daylight. Dark, controllable, and secret. ”
    “Deep-downers in a nutshell,” said Vimes.
    “This is very exciting!” said Sir Reynold. “And they dug into the cellars of my museum?”
    “Over to you, Fred,” said Vimes, carefully drawing a line across the map.
    “Er, right,” said Fred Colon. “Er…Nobby an’ me found out where only a couple of hours ago,” he said, thinking it wisest not to add “after Mister Vimes yelled at us and made us tell him every last detail and then sent us back and told us what to look for.” What he did add was: “They were pretty clever, sir. The mortar even looked dirty. I bet you’re saying to yourself, ahah, sir?”
    “I am?” said Sir Reynold, bewildered. “I hwould normalleah say ‘my goodness.’ ”
    “I expect you’re saying to yourself, ahah, how were they able to build up the wall again after they’d got the muriel out, sir, and we reckon—”
    “hWell, I imagine one dwarf stayed behind to make good, lay low, as you hwould say, and hwandered out in the morning,” said Sir Reynold. “There hwere people going in and out all the time. hWe hwere looking for a big painting, after all, not a person.”
    “Yessir. We reckon one dwarf stayed behind to make good, lay low, and wandered out in the morning. There were people going in and out all the time. You were looking for a big painting, after all, not a person,” said Fred Colon. He’d been very pleased to come up with that theory, so he was going to say it out loud no matter what.
    Vimes tapped the map. “And here, Sir Reynold, is where a troll called Brick fell through another cellar floor into their tunnel,” he said. “He also told us he saw something in the main mine, which sounds very much like the Rascal.”
    “But, alas, you have not found it,” said Sir Reynold.
    “I’m sorry, sir. It’s probably long gone out of the city.”
    “But hwhy?” said the curator. “They could have studied it in the museum! hWe’re very interactive these days!”
    “Interactive?” said Vimes. “What do you mean?”
    “hWell, people can…look at the pictures as much as they hwant,” said Sir Reynold. He sounded a little annoyed. People shouldn’t ask that kind of question.
    “And the pictures do what, exactly?”
    “Er…hang there, Commander,” said Sir Reynold. “Of course.”
    “So what you mean is, people can come and look at the pictures, and the pictures, for their part, are looked at?”
    “Rather like that, yes,” said the curator. He thought for a moment, aware that this probably wasn’t sufficient, and added: “But