Guards! Guards!

was the way he could roll his upper lip back to reveal more incredibly yellow teeth than any other mouth the University Council had ever seen before that somehow made sure the matter was never really raised.
    But now there was another sound, the alien sound of a door creaking open. Footsteps padded across the floor and disappeared among the clustering shelves. The books rustled indignantly, and some of the larger grimoires rattled their chains.
    The Librarian slept on, lulled by the whispering of the rain.
    In the embrace of his gutter, half a mile away, Captain Vimes of the Night Watch opened his mouth and started to sing.

    Now a black-robed figure scurried through the midnight streets, ducking from doorway to doorway, and reached a grim and forbidding portal. No mere doorway got that grim without effort, one felt. It looked as though the architect had been called in and given specific instructions. We want something eldritch in dark oak, he’d been told. So put an unpleasant gargoyle thing over the archway, give it a slam like the footfall of a giant and make it clear to everyone, in fact, that this isn’t the kind of door that goes “ding-dong” when you press the bell.
    The figure rapped a complex code on the dark woodwork. A tiny barred hatch opened and one suspicious eye peered out.
    “‘The significant owl hoots in the night,’” said the visitor, trying to wring the rainwater out of its robe.
    “‘Yet many gray lords go sadly to the masterless men,’” intoned a voice on the other side of the grille.
    “‘Hooray, hooray for the spinster’s sister’s daughter,’” countered the dripping figure.
    “‘To the axeman, all supplicants are the same height.’”
    “‘Yet verily, the rose is within the thorn.’”
    “‘The good mother makes bean soup for the errant boy,’” said the voice behind the door.
    There was a pause, broken only by the sound of the rain. Then the visitor said, “What?”
    “‘The good mother makes bean soup for the errant boy.’”
    There was another, longer pause. Then the damp figure said, “Are you sure the ill-built tower doesn’t tremble mightily at a butterfly’s passage?”
    “Nope. Bean soup it is. I’m sorry.”
    The rain hissed down relentlessly in the embarrassed silence.
    “What about the cagèd whale?” said the soaking visitor, trying to squeeze into what little shelter the dread portal offered.
    “What about it?”
    “It should know nothing of the mighty deeps, if you must know.”
    “ Oh , the cagèd whale . You want the Elucidated Brethren of the Ebon Night. Three doors down.”
    “Who’re you, then?”
    “We’re the Illuminated and Ancient Brethren of Ee.”
    “I thought you met over in Treacle Street,” said the damp man, after a while.
    “Yeah, well. You know how it is. The fretwork club have the room Tuesdays. There was a bit of a mix-up.”
    “Oh? Well, thanks anyway.”
    “My pleasure.” The little door slammed shut.
    The robed figure glared at it for a moment, and then splashed further down the street. There was indeed another portal there. The builder hadn’t bothered to change the design much.
    He knocked. The little barred hatch shot back.
    “Yes?”
    “Look, ‘The significant owl hoots in the night,’ all right?”
    “‘Yet many gray lords go sadly to the masterless men.’”
    “‘Hooray, hooray for the spinster’s sister’s daughter,’ okay?”
    “‘To the axeman, all supplicants are the same height.’”
    “‘Yet verily, the rose is within the thorn.’ It’s pissing down out here. You do know that, don’t you?”
    “Yes,” said the voice, in the tones of one who indeed does know it, and is not the one standing in it.
    The visitor sighed.
    “‘The cagèd whale knows nothing of the mighty deeps,’” he said. “If it makes you any happier.”
    “‘The ill-built tower trembles mightily at a butterfly’s passage.’”
    The supplicant grabbed the bars of the window, pulled himself up to it, and hissed: “Now let us in, I’m soaked.”
    There was another damp pause.
    “These deeps…did you say mighty or nightly?”
    “Mighty, I said. Mighty deeps. On account of being, you know, deep. It’s me, Brother Fingers.”
    “It sounded like nightly to me,” said the invisible doorkeeper cautiously.
    “Look, do you want the bloody book or not? I don’t have to do this. I could be at home in bed.”
    “You sure it was mighty?”
    “Listen, I know how deep the bloody deeps are all