the Professor was still alive?"

"Why, yes, sir; of course I couldn't say so surely. I thought he
was reading or writing, but oh, dear Lord! there he was this morning,
nearly twelve hours later, in just the same position." Johann
shivered at the thought that he might have seen his master sitting
at his desk, already a corpse.

"He must have been dead when you came home. Don't you think the
sound of that shot would have wakened you?"

"Yes, sir, I think likely, sir," murmured Johann. "But if the
murderer could get into the house, how could he get into the
apartment?"

"There must have been a third key of which you knew nothing,"
answered Horn, turning to Muller again. "It's stranger still how
Fellner could have been shot, for the window-shutters were fastened
and quite uninjured, and both doors were locked on the inside."

As he said these words, Horn looked sharply at his subordinate; but
Muller's calm face did not give the slightest clue to his thoughts.
The experienced police commissioner was pleased and yet slightly
angered at this behaviour on the part of the detective. He knew
that it was quite possible that Muller had already formed a clear
opinion about the case, and that he was merely keeping it to himself.
And yet he was glad to see that the little detective had apparently
learned a lesson from his recent mistake concerning the death of
Mrs. Kniepp - that he had somewhat lost confidence in his hitherto
unerring instinct, and did not care to express any opinion until he