A woman coming down the street, swinging a chatelaine, walked close to him, spoke, and for a moment they talked.

“It’s the gun-moll,” remarked Kennedy.  “She’s getting Brodie off his guard.  This must be the root of that grapevine system, as they call it.”

Suddenly from the shadow of the next house a stealthy figure sprang out on Brodie.  It was our dip, a dip no longer but a regular stick-up man, with a gun jammed into the face of his victim and a broad hand over his mouth.  Skilfully the woman went through Brodie’s pockets, her nimble fingers missing not a thing.

“Now—­beat it,” we heard the dip whisper hoarsely, “and if you raise a holler, we’ll get you right, next time.”

Brodie fled as fast as his weakened nerves would permit his shaky limbs to move.  As he disappeared, the dip sent something dark hurtling over the roof of the house across the street and hurried toward us.

“What was that?” I asked.

“I think it was the pistol on the end of a stout cord.  That is a favourite trick of the gunmen after a job.  It destroys at least a part of the evidence.  You can’t throw a gun very far alone, you know.  But with it at the end of a string you can lift it up over the roof of a tenement.  If Brodie squeals to a copper and these people are caught, they can’t hold them under the pistol law, anyhow.”

The dip had caught sight of us, with his ferret eyes in the doorway.  Quickly Kennedy passed over the money in return for the motley array of objects taken from Brodie.  The dip and his gun-moll disappeared into the darkness as quickly as they had emerged.

There was a curious assortment—­the paraphernalia of a drug fiend, old letters, a key, and several other useless articles.  The pickpocket had retained the money from the sale of the dope as his own particular honorarium.

“Brodie has led us up to the source of his supply,” remarked Kennedy, thoughtfully regarding the stuff.  “And the dip has given us the key to it.  Are you game to go in?”

A glance up and down the street showed it still deserted.  We wormed our way in the shadow to the cellar before which Brodie had stood.  The outside door was open.  We entered, and Craig stealthily struck a match, shading it in his hands.

At one end we were confronted by a little door of mystery, barred with iron and held by an innocent enough looking padlock.  It was this lock, evidently, to which the key fitted, opening the way into the subterranean vault of brick and stone.

Kennedy opened it and pushed back the door.  There was a little square compartment, dark as pitch and delightfully cool and damp.  He lighted a match, then hastily blew it out and switched on an electric bulb which it disclosed.

“Can’t afford risks like that here,” he exclaimed, carefully disposing of the match, as our eyes became accustomed to the light.

On every side were pieces of gas-pipe, boxes, and paper, and on shelves were jars of various materials.  There was a work-table littered with tools, pieces of wire, boxes, and scraps of metal.