«Greetings, honored hoodlum,» Wheezle whispered in Petrov's ear. «We would not hurt you for the world, but you have accidentally sat where Mr. Cavendish is about to thrust his sword. I suggest you keep very, very still.»

Wheezle assigned four wights to hold Petrov down, a number which struck me as excessive. True, old Bleach-Hair was a bulky brawler of a berk, and on a good night he could sling a pair of tavern wenches under each arm; but at the moment, a five-year-old with sharp fingernails could drop Petrov to his knees by poking the man's frostbitten tum-tum.

«Should he really be moaning like that?» Hezekiah asked. «I think he's hurt.»

«He wants us to let down our guard,» I said, as the wights slammed our captive onto the hard metal table. The jarring sound of impact was quickly replaced by a wail of agony from Petrov. «He's such a big baby,» I muttered.

Wheezle clambered up on a chair so he could lift himself to eye level with the man. «Now, honored hoodlum,» he said, «we would like to know what happened to our colleagues: the ones you confronted back at the Vertical Sea.»

«The sodding berks froze my hide off!» he growled. «But I got my revenge – showed them what a haunch of beef feels like inside the oven.»

I let the tip of my rapier nestle down against his Adam's apple. «Did you kill them?»

«I piking well wanted to… but Qi and Chi said no, Rivi would want to question them.»

«So all three are alive?»

«They were the last time I saw them. Not pretty,» he added with a leer, «but alive.»

With miniscule effort, I could have leaned forward and sent the bladepoint through his windpipe. Not pretty, but alive… the words flooded like poison into my heart. Petrov and his cronies had been carrying firewands as they fought our friends. I thought of Yasmin looking as savagely burnt as the victims in the court rotunda; and I had to walk away quickly before I forgot myself.

«Who are Qi and Chi?» I heard Hezekiah asking.

«Thieves. A githzerai and githyanki – they helped bring down your pus-swilling friends. While the boys and I made things toasty up front, Qi and Chi snuck up from behind and tickled some spines with steel. Your group surrendered nice and quiet once they'd been ventilated a bit.»

«Where are our teammates now?» Wheezle asked.

«Go pike yourself.» Petrov aimed some spittle in Wheezle's general direction. He got more on himself than he did on the gnome, but it was the thought that counted. «I've said enough already,» Petrov snarled, «and I'm not rattling my bone-box no more.»

«Dear, oh dear,» I tsked from the corner of the room, «torture time again. Hezekiah,» I raised my voice, «what faction do you think boasts the most fearsome torturers?»

«Ummm… the Mercykillers?»

«Not a bad guess,» I told him. «The Mercykillers like torturing people and they put a lot of effort into it… but alas, they're overly crude. They're too fond of breaking bones and spilling blood; they haven't devoted themselves to discovering what genuinely causes the maximum amount of pain. The true students of excruciation are… well, I blush to admit it, but the most adept torturers in the multiverse belong to my own faction, the Sensates.»

«You're a Sensate?» Petrov asked uneasily.

«That's right,» I answered, stepping up to the table. «We've spent centuries documenting every possible sensation the human body can experience. Many people think we only pursue pleasure, but that's wrong. We devote equal time to the study of pain. To the science of pain. For example, let me try to remember the location of the capitus nerve.»

I leaned over Petrov's body and drew out my tweak-knife. It was not an imposing blade, just a tiny thing I kept for whittling pen nibs when I wanted to sketch in ink; but it had a good sharp edge that I'd whetted less than a week earlier. In a pinch, it could double as a razor.

«The capitus nerve,» I said, making up the story as I went along, «runs all the way from the ball of the right foot to the left lobe of the brain.» I drew the unsharpened side of the blade up the length of Petrov's body. «Did you know that the longer the nerve is, the more pain it can experience? And the capitus nerve is the longest nerve in the body.»

«Who the sod cares?» Petrov snapped.

«I, for one, find it most stimulating,» Wheezle replied. «Please continue, honored Cavendish.»

«The capitus nerve runs through the most pain-sensitive areas of the anatomy. The knee. The inside of the thigh. The groin, of course.» I tapped each of these lightly with the flat of the blade. «Then there's the chest, which I notice is already in a tender condition. There's a great deal of individual variation in the route of the capitus through the chest, but you can usually find it by cross-correlating with a few other key meridians. First you find the small intestine…»

I jabbed my thumb deep into the pit of Petrov's stomach. He shrieked, probably thinking I was using the knife; or maybe he was reacting to true agony, from the frostbitten skin of his gut. «Ohh,» I said with great sympathy, «if you think that hurt, you're in trouble. The nerve I just hit was an itty-bitty one… scarcely able to feel pain at all. About the same size as this one.»

Extending a knuckle, I rubbed briskly along the man's sternum, raking back and forth across a knot of nerves I happened to know lurked there just under the skin. Petrov howled again. I wiped off my knuckle; flakes of chapped skin had stuck to it when it pulled away from Petrov's breastbone.

«Well, those two points of reference have given me a bearing on where the capitus nerve should be,» I told him. Lifting my knife, I added, «It may take some digging to hit the nerve bang-on, but I guarantee it will be worth the wait.» I leaned in toward one of the wights who was holding Petrov down. «Could you tilt his head so it's pointing away from me? They always vomit when I do this, and I don't have a change of clothes.»

«All right!» Petrov yelled. «Who the pike cares? I'll take you where the rotten sods are locked up.»

A few seconds ticked away in silence; then Wheezle touched my sleeve. «Could you show me where the capitus nerve is anyway? I would be most interested in learning.»

Wordlessly, I shook my head.

More corridors to slog through, and time was ticking by. I wondered how long it would be till Rivi's wights found the grinders out in the arena of dust. There was no way to guess. If I were a true hero like my father, maybe I'd be racing after Rivi and the Fox instead of Yasmin: putting the fate of the multiverse ahead of a few individuals. We had Unveiler and could command the wights to attack our enemies. Unfortunately, the wights would all be wandering in the airless arena, where they couldn't hear us calling orders; meanwhile, we'd face a fire-mage and a mind-raper, plus their band of bully-bashers armed with flame-wands.

No, I decided, my father might have succeeded against such a mass of enemies, but I couldn't handle the odds. Saving Yasmin and the others was at least manageable. Once we rescued our friends, we could hightail it back to Sigil and fetch reinforcements. It wasn't a heroic plan, but it was something we might survive.

In time, I heard telltale sounds of clanking up ahead and Petrov led us into another machinery room, twin to the previous one. Obviously, the Glass Spider had several independent drive mechanisms, each with its own engine room; a separate motor for each of the Spider's legs. This machine room had the same number of pistons chugging away, the same layout, the same noise… but the control bunker in the corner had a huge wooden beam blocking the door shut.

«They're in there,» Petrov pointed to the door. «Gods rot you all.»

«Amen,» Wheezle agreed earnestly.

Three wights held Petrov, one held Miriam, and the other four went to work moving the beam. Judging from the way they strained, I estimated the timber weighed close to a ton. It took the wights a full minute to get the beam clear of the door, and in that time Hezekiah made a discovery: Oonah's ice-staff, tucked in under a desk whose surface glowed with incomprehensible runes of light.