"He must have died at once, without suffering," said the physician.

"He killed himself—he killed himself," murmured Johann, as if bewildered.

"It's strange that he should have found time to lay down the revolver before he died," remarked Horn. Johann put out his hand and raised the weapon before Horn could prevent him. "Leave that pistol where it was," commanded the commissioner. "We have to look into this matter more closely."

The doctor turned quickly. "You think it was a murder?" he exclaimed. "The doors were both locked on the inside—where could the murderer be?"

"I don't pretend to see him myself yet. But our rule is to leave things as they are discovered, until the official examination. Muller, did you shut the outer door?"

"Yes, sir; here is the key."

"Johann, are there any more keys for the outer door?"

"Yes, sir. One more, that is, for the third was lost some months ago. The Professor's own key ought to be in the drawer of the little table beside the bed."

"Will you please look for it, Muller?"

Muller went into the bedroom and soon returned with the key, which he handed to the commissioner. The detective had found something else in the little table drawer—a tortoise-shell hairpin, which he had carefully hidden in his own pocket before rejoining the others.

Horn turned to the servant again. "How many times have you been out of the apartment since last night?"

"Once only, sir, to go to the police station to fetch you."

"And you locked the door behind you?"

"Why, yes, sir. You saw that I had to turn the key twice to let you