"He was killed by a bullet，" said Muller.

　　"Yes， that was it，" replied the doctor. With the raising of the body the dead man's waistcoat fell back into its usual position， and they could see a little round hole in his shirt. The doctor opened the shirt bosom and pointed to a little wound in the Professor's left breast. There were scarcely three or four drops of blood visible. The hemorrhage had been internal.

　　"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 in."

　　Horn and Muller both looked the young man over very carefully. He seemed perfectly innocent， and their suspicion that he might have turned the key in pretense only， soon vanished. It would have been a foolish suspicion anyway. If he were in league with the murderer， he could have let the latter escape with much more safety during the night. Horn let his eyes wander about the rooms again， and said slowly： "Then the murderer is still here - or else - "

　　"Or else？" asked the doctor.

　　"Or else we have a strange riddle to solve."

　　Johann had laid the pistol down again. Muller stretched forth his hand and took it up. He looked at it a moment， then handed it to the commissioner. "We have to do with a murder here. There was not a shot fired from this revolver， for every chamber is still loaded. And there is no other weapon in sight，" said the detective quietly.

　　"Yes， he was murdered. This revolver is fully loaded. Let us begin the search at once." Horn was more excited than he cared to show.

　　Johann looked about in alarm， but when he saw the others beginning to peer into every corner and every cupboard， he himself joined in the man-hunt. A quarter of an hour later， the four men relinquished their fruitless efforts and gathered beside the corpse again.

　　"Doctor， will you have the kindness to report to the head Commissioner of Police， and to order the taking away of the body？ We will look about for some motive for this murder in the meantime，" said Horn， as he held out his hand to the physician.

　　Muller walked out to the door of the house with the doctor.

　　"Do you think this valet did it？" asked the physician softly.

　　"He？ Oh， dear， no，" replied the detective scornfully.

　　"You think he's too stupid？ But this stupidity might be feigned."

　　"It's real enough， doctor."

　　"But what do you think about it - you， who have the gift of seeing more than other people see， even if it does bring you into disfavour with the Powers that Be？"

　　"Then you don't believe me yet？"

　　"You mean about the beautiful Mrs. Kniepp？

　　"And yet I tell you I am right. It was an intentional suicide."

　　"Muller， Muller， you must keep better watch over your imagination and your tongue！ It is a dangerous thing to spread rumours about persons high in favor with the Arch-duke. But you had better tell me what you think about this affair，" continued the doctor， pointing back towards the room they had just left.

　　"There's a woman in the case."

　　"Aha！ you are romancing again. Well， they won't be so sensitive about this matter， but take care that you don't make a mistake again， my dear Muller. It would be likely to cost you your position， don't forget that."

　　The doctor left the house. Muller smiled bitterly as he closed the door behind him， and murmured to himself： "Indeed， I do not forget it， and that is why I shall take this matter into my own hands. But the Kniepp case is not closed yet， by any means."

　　When he returned to the study he saw Johann sitting quietly in a corner， shaking his head， as if trying to understand it all. Horn was bending over a sheet of writing paper which lay before the dead man. Fellner must have been busy at his desk when the bullet penetrated his heart. His hand in dying had let fall the pen， which had drawn a long black mark across the bottom of the sheet. One page of the paper was covered with a small， delicate handwriting.

　　Horn called up the detective， and together they read the following words：

　　"Dear Friend： -

　　"He challenged me - pistols - it means life or death. My enemy is very bitter. But I am not ready to die yet. And as I know that I would be the one to fall， I have refused the duel. That will help me little， for his revenge will know how to find me. I dare not be a moment without a weapon now - his threats on my refusal let me fear the worst. I have an uncanny presentiment of evil. I shall leave here to-morrow. With the excuse of having some pressing family affair to attend to， I have secured several days' leave. Of course I do not intend to return. I am hoping that you will come here and break up my establishment in my stead. I will tell you everything else when I see you. I am in a hurry now， for there is a good deal of packing to do. If anything should happen to me， you will know who it is who is responsible for my death. His name is - "

　　Here the letter came to an abrupt close.

　　Muller and Horn looked at each other in silence， then they turned their eyes again toward the dead man.

　　"He was a coward，" said the detective coldly， and turned away. Horn repeated mechanically， "A coward！" and his eyes also looked down with a changed expression upon the handsome， soft-featured face， framed in curly blond hair， that lay so silent against the chair-back. Many women had loved this dead man， and many men had been fond of him， for they had believed him capable and manly.