That night, in the swollen dark hours after a brief spew of rain had hosed the city down with dirty water, the door to Isaac’s warehouse was pushed open. The street was empty. There were minutes of stillness. Night-birds and bats were all that moved. Gaslight guttered.

The construct rolled jerkily out into the deep night. Its valves and pistons were swathed in rags and snatches of blankets, muffling the distinctive sound of its passage. It moved forward quickly, turning inexactly and trundling as fast as its ageing treads would move.

It tremored through the backstreets, passed snoring drunks still sodden and insensate. The sallow gasjets reflected secretively in its battered metal hide.

The construct made its swift, precarious way under the skyrails. Inconstant streaks of cirrus hid the lurking airships. The construct bore down like a diviner on the Tar, the river caught in an intricate whiplash shape on the timeless rocks beneath the city.

And hours after it had disappeared over Sheer Bridge into the southern city, when the dark sky became stained by dawn, the construct came reeling back to Brock Marsh. Its timing was fortuitous. It re-entered and locked the door only a little while before Isaac returned from his frantic night-long search for David, and Lin, and Yagharek and Lemuel Pigeon, and anyone who could help him.

Lublamai was lying on a couch that Isaac had rigged up on a couple of chairs. When Isaac came into the warehouse he came straight over to his still friend, whispered to him hopelessly, but there was no change. Lublamai did not sleep or wake. He gazed.

It was not long before David came hurrying back to the laboratory. He had trawled his way to one of his usual haunts to be greeted by a hurried and garbled version of one of the innumerable messages Isaac had left for him throughout New Crobuzon.

He sat as silently as Isaac, gazing at his mindless friend.

“I can’t believe I let you do it,” he said numbly.

“Oh Jabber and fuck, David, d’you think I’m not going over and over it . . . I let the damn thing out . . .”

“We all should’ve known better,” snapped David.

There was a long silence between them.

“Did you get a doctor?” said David.

“First thing I did. Phorgit, from across the road, I’ve dealt with him before. I cleaned up Lub a bit, wiped some of that crap off his face . . . Phorgit didn’t know what to make of it. Plugged in gods knows how many bits of equipment, took I don’t fucking remember how many readings . . . boils down to ‘haven’t got a clue.’ ‘Keep him warm and feed him, but then again you might want to keep him cold and not give him anything to eat . . .’ I might get one of the guys I know at the uni to take a skedge at him, but it’s a forlorn fucking hope . . .”