The words, courteous in themselves, conveyed to the hearer an impression of biting sarcasm.
"I found the parlor already occupied; I hesitated to disturb a tête-à-tête," replied Sturgis quietly.
Murdock eyed him narrowly for a moment, and then invited him into the study.
The chemist's study was a spacious room, plainly but luxuriously furnished, and containing every convenience and comfort calculated to lighten the labor of a busy man. The table, littered with books and papers, stood near a small safe and almost directly opposite the hall door. Speaking-tubes and electric call buttons were within reach of the occupant of the easy chair, and probably placed him in communication with the various portions of the household; while a telephone on one side and a typewriter on the other showed that the chemist kept in touch also with the outside world.
Murdock's interlocutor, whoever he had been, had disappeared. But how? The question interested Sturgis, and his mind at once began to seek an answer to it.
There were three doors leading from the study. One of these was the one by which Murdock and Sturgis had just entered from the hall. No one could have passed out that way without meeting them.
Then there were the folding-doors leading into the library; but, as the door leading from the library to the hall had remained slightly ajar, Sturgis felt sure that he would have heard the man had he gone out by that way.
The third door led to a small extension.
"He must have gone into the extension," thought Sturgis.
The only alternative was an exit through the windows. This in itself would not have presented any special difficulty; for the distance to the flagging below was hardly more than twelve or thirteen feet. But the yard, which was of diminutive size on account of the space allotted to the garden on the street, was inclosed by an unusually high fence protected by a row of sharp and closely set spikes. These looked so formidable that the thought of any one attempting to scale the fence instantly suggested visions of impaled wretches writhing in Oriental tortures. The only possible exit from the yard, therefore, seemed to be through the basement; that is to say, past the kitchen and the servants' department.