A mounted policeman galloped past us, blazing away at the tires.  The avenue was stirred, as seldom even in its strenuous life, with reports of shots, honking of horns, the clang of trolley bells and the shouts of men.

The pursuers were losing when there came a rattle and roar from the rear wheels which told that the tires were punctured and the heavy car was riding on its rims.  A huge brewery wagon crossing a side street paused to see the fun, effectually blocking the road.

The car jolted to a stop.  The chauffeur leaped out and a moment later dived down into a cellar.  In that congested district, pursuit was useless.

“Only an accomplice,” commented Kennedy.  “Perhaps we can get him some other way if we can catch the man—­or woman—­higher up.”

Down the street now we could see Garwood surrounded by a curious crowd but in possession of the car.  I looked about for Duncan and Reginald.  They had apparently been swallowed up in the crowds of idlers which seemed to be pouring out of nowhere, collecting to gape at the excitement, after the manner of a New York crowd.

As I ran my eye over them, I caught sight of Reginald near the corner where we had left him in an incipient fight with someone who had a fancied grievance.  A moment later we had rescued him.

“Where’s Duncan?” he panted.  “Did anything happen to him?  Garwood told us to stay here—­but we got separated.”

Policemen had appeared on the heels of the crowd and now, except for a knot following Garwood, things seemed to be calming down.

The excitement over, and the people thinning out, Kennedy still could not find any trace of Duncan.  Finally he glanced in again through the swinging doors.  There was Duncan, evidently quite upset by what had occurred, fortifying himself at the bar.

Suddenly from above came a heavy thud, as if someone had fallen on the floor above us, followed by a suppressed shuffling of feet and a cry of help.

Kennedy sprang toward a side door which led out into the hall to the hotel room above.  It was locked.  Before any of the others he ran out on the street and into the hall that way, taking the stairs two at a time, past a little cubby-hole of an “office” and down the upper hall to a door from which came the cry.

It was a peculiar room into which we burst, half bedroom, half workshop, or rather laboratory, for on a deal table by a window stood a rack of test-tubes, several beakers, and other paraphernalia.

A chambermaid was shrieking over a woman who was lying lethargic on the floor.

I looked more closely.

It was Dora Sears.

For the moment I could not imagine what had happened.  Had the events of the past few days worked on her mind and driven her into temporary insanity?  Or had the blackmailing gang of automobile thieves, failing in extorting money by their original plan, seized her?