the war he was temporarily under suspicion for sympathies with
the enemy, but no proof was adduced of his enmity and, though he had
undoubtedly been born on the wrong side of the Border at Cranenburg,
which is the Prussian frontier station on the Rotterdam-Cologne line,
his name was undoubtedly van Heerden, which was Dutch. Change the "van"
to "von," said the carping critics, and he was a Hun, and undoubtedly
Germany was full of von Heerens and von Heerdens.

The doctor lived down criticism, lived down suspicion, and got together
a remunerative practice. He had the largest flat in the building, one
room of which was fitted up as a laboratory, for he had a passion for
research. The mysterious murder of John Millinborn had given him a
certain advertisement which had not been without its advantages. The
fact that he had been in attendance on the millionaire had brought him a
larger fame.

His theories as to how the murder had been committed by some one who had
got through the open window whilst the two men were out of the room had
been generally accepted, for the police had found footmarks on the
flowerbeds, over which the murderer must have passed. They had not,
however, traced the seedy-looking personage whom Mr. Kitson had seen.
This person had disappeared as mysteriously as he had arrived.

Three months after the murder the doctor stood on the steps of the broad
entrance-hall which led to the flats, watching the stream of pedestrians
passing. It was six o'clock in the evening and the streets were alive
with shop-girls and workers on their way home from business.

He smoked a cigarette and his interest was, perhaps, more apparent than
real. He had attended his last surgery case and the door of the "shop,"
with its sage-green windows, had been locked for the night.

His eyes wandered idly to the Oxford Street end of the thoroughfare, and
suddenly he started. A girl was walking toward him. At this hour there
was very little wheeled traffic, for Lattice Street is almost a
cul-de-sac, and she had taken the middle of the road. She was dressed
with that effective neatness which brings the wealthy and the work-girl
to a baffling level, in a blue serge costume of severe cut; a plain
white linen coat-collar and a small hat, which covered, but did not
hide, a mass of hair which, against the slanting sunlight at her back,
lent the illusion of a golden nimbus about her head.

The eyes were deep-set and wise with the wisdom wh