sharp to the right in Store Street, and pull up. I'll tell you when to
go on again."

The man obeyed. Theydon posted himself at the outer window, and in a
space of time so short that the excellence of the gray car's
accelerator was amply demonstrated, the pursuer swung into sight. A
stolid-faced chauffeur at the wheel did not appear discomfited at
coming on his quarry thus unexpectedly. He whirled past, seemingly
quite oblivious of Theydon's fixed stare. Though the weather was mild
he wore an overcoat with upturned collar, so that between its
protecting flaps and a low-peaked cap his face was well hidden. Still,
Theydon received an impression of a curiously wooden physiognomy.

The man might have been an automaton for all the heed he gave to the
taxi or its inquisitive occupant. But his aspect was almost forgotten
in the far stranger discovery that the car was empty. Both windows
were open, and the bright lights of a corner shop flashed into the
interior, yet not a soul was visible. Moreover, the car sped on
unhesitatingly, stopping some two hundred yards ahead.

So far as Theydon could tell, no one alighted. He jotted down the
number-- XY 1314-- on his shirt cuff.

"Did you happen to see that car waiting near the house I came from?"
he said to the taxi man, who, of course, provided an interested
audience of one.

"Yes, sir," was the ready answer. "It's not a London car. I've never
seen them letters afore."