There was a note of savagery in his voice which made her turn sick.

For a second she filled her lungs to scream, but at that instant a mass
of cotton-wool was thrust over her face, and she began to breathe in a
sickly sweet vapour. Somebody else was in the room now. They were
holding her feet. The voice in her ear said:

"Breathe. Take a deep breath!"

She sobbed and writhed in an agony of mind, but all the time she was
breathing, she was drawing into her lungs the chloroform with which the
wool was saturated.

At two o'clock in the morning a uniformed constable, patrolling his
beat, saw an ambulance drawn up outside a house in Doughty Street. He
crossed the road to make inquiries.

"A case of scarlet fever," said the driver.

"You don't say," said the sympathetic constable.

The door opened and two men walked out, carrying a figure in a blanket.
The policeman stood by and saw the "patient" laid upon a stretcher and
the back of the ambulance closed. Then he continued his walk to the
corner of the street, where he found, huddled up in a doorway, the
unconscious figure of a Scotland Yard detective, whose observation had
been interrupted by a well-directed blow from a life preserver.

CHAPTER XV

THE COMMISSIONER HAS A THEORY

"To all stations. Stop Ambulance Motor No. LKO 9943. Arrest and detain
driver and any person found therein. Warn all garages and
report.--COMMISSIONER."

This order flashed from station to station throughout the night, and
before the dawn, nine thousand policemen were on the look-out for the
motor ambulance.

"There's a chance, of course," said Stafford, "but it is a poor chance."

He was looking white and heavy-eyed.

"I don't know, sir," said Southwick, his subordinate. "There's always a
chance that a crook will do the obviously wrong thing. I suppose you've
no theory as to where they have gone?"

"Not out of town--of that I'm certain," said King, "that is why the
quest is so hopeless. Why, they'll have got to their destination hours
before the message went out!"

They were standing in the girl's bedroom, which still reeked with
chloroform, and all the clues were piled together on the table. There
were not many. There was a pad of cotton-wool, a half-empty bottle of
chloroform, bearing the label of a well-known wholesaler, and one of a
pair of old wash-leather gloves, which had evidently been worn by
somebody in his desire to avoid leaving finger-prints.

"We've not