Mel Colly was found dead in his library. His forehead was resting on the keys of a tape recorder, a pool of blood lay on the desk beside him. From the door, Shadow could see that Mel's right hand covered the gun and that a bullet had entered his right temple. Shadow removed the tape recorder from under Mel's head and pressed the play button. A voice said,"This is Mel Colly speaking. I am not going to go on with a long winded farewell. I'm tired of life and all its anguish. I'll see you on the other side, wherever that may be." There was a gunshot and the sound of his head hitting the tape recorder keys, followed by a click indicating the tape recorder had been shut off. Shadow was certain that someone else had imitated Mel's voice and made this recording to sound like a suicide. Why does Shadow suspect murder?