The “Webbs” had moved in ten days before; their furniture having been carefully selected in different secondhand stores of the better class.

Charles Webb, the “father,” went downtown every day, but it was understood in the neighborhood that “Will” was temporarily out of work. That explained why he remained at home all day.

A close but secret watch had been kept on the doctor’s house, and its regular occupants had been studied as thoroughly as possible under the circumstances.

Doctor Siebold, Grantley’s assistant, had proved to be a man in his early thirties, evidently of German descent, whose keen, searching eyes seemed to belie his too agreeable expression and his suave manners.

Kate Rawlinson, the nurse, seemed to be thoroughly efficient, as she must have been to please Doctor Grantley; but her face, which was rather good looking, in a pinched, tight-lipped way, had a hard, forbidding expression, which warned one not to look to her for much human sympathy, to say the least.

As for Hoff, the German servant, Nick found it easy to agree with Wallace that he had been a soldier. He was fully six feet in height, powerfully built, with a scarred face, keen blue eyes, and a sandy mustache, the points of which were trained rakishly upward, after the model of his emperor’s.

Of the lot, he was the only one who seemed likely to give much trouble in a physical encounter, if it came to that. Siebold was slight and wore glasses, and Doctor Grantley himself, while undoubtedly strong and wiry, did not impress one as a fighting man.

That remained to be seen, however.

It was Hoff who always answered the door, and he did it with an air of suspicion and a brusqueness which suggested a sentry on duty.

Little real progress had been made by the detectives, despite their vigilance. They had discovered that Wallace was correct in saying that patients who seemed to be in humble circumstances were frequently brought to Doctor Grantley’s, or came of their own accord, and they had verified Wallace’s report that several young men, obviously doctors, frequented the place, but that had only been ascertained after a tedious wait.