"You are certain?" Hester said to the handsome, weary woman busy sewing shirts. All the time she was talking to them her fingers never stopped. She barely needed to look at what she was doing.

"Course I am. Don' forget summink like a young lady, an' she were a lady, comin' an' askin' about sewers an' drains an' water wot runs under the ground. Knowed about it, too, she did-engines, too. Knew one from another."

Rose stiffened, glancing at Hester, then back at the woman.

"She knew about underground streams?" Hester asked, trying to keep the urgency out of her voice.

"Summink," the woman replied. "Queer, though." She shook her head. "She wanted ter know more. I said me pa'd bin a tosher, afore 'e got took, an' she wanted ter know if I still knew any toshers now. Or gangers. I tol' 'er me bruvver were a tosher, but I in't seen 'im in years. She asked me 'is name. Now wot'd a nice young lady like that wanna find a tosher fer?"

"To learn more about hidden streams?" Rose suggested.

The woman's eyes opened wide. "Wot fer? Yer don' think one o' them's gonna break through, do yer?"

"Did she say that?"

"No! Course she din't! D'yer think I'd be sittin' 'ere wi' a needle in me 'and if she 'ad? Me sister's 'usband's down there diggin'." She made no reference to her own husband, one-armed, who was out somewhere in the streets trying to earn a living running errands for people. "Is this wot yer on about? Wot 'appened to 'er, anyway? Why are yer 'ere?"

Hester debated only for an instant. "She fell off Westminster Bridge and drowned. We are concerned it may not have been an accident. We need to know what she learned."

"Nothin' from 'ere that'd get her topped, I swear that on me muvver's grave!

They stayed another ten minutes, but the woman could add nothing.

Outside it was dark and the snow was beginning to accumulate, even though it was only shortly after six.

"Do you suppose she went looking for toshers?" Rose said unhappily. "What for? To tell her where the underground streams were? Surely Argyll would have done all that. He can't want a disaster-it would ruin him most of all."

"I don't know," Hester admitted, beginning to walk towards the omnibus stop. Moving was better than standing still. "It doesn't make any sense, and she must have known that. But she learned something. What could it be, other than that they are somehow using the machines dangerously, in order to be the fastest, and therefore get the best contracts? Are Argyll's machines different from other people's? We need to find out. Could they be more dangerous?"

Rose stopped, shuddering with cold. "It seems they work faster-so maybe they are. What can we do? These men won't tell us anything-they daren't!" There was anguish in her cry.