"You murderer!" Paul Harker’s voice whispered words seemed to ring through the room, and with a little strangled gasp a woman fainted. The doctor’s face, grim and accusing, was turned on Billy, as if demanding some explanation which he knew full well could not be given. And of all those present only Billy Merton himself seemed cool and calm, as, with his hands still in his pockets, he faced the ring of his accusers. "What have you to say?" said the doctor, sternly. "One thing—and one thing only," answered Billy. "I have read in fiction of diabolical plots: to-night I have met one in real life. But, as so often happens in fiction, one mistake is made, which leads to the undoing of the villain. And one mistake has been made to-night." And now his eyes, merciless and stern, were fixed on Paul Harker, and he noticed with a certain grim amusement that a muscle in the millionaire’s face was beginning to twitch. "Mr. Harker is a man of nerve: he also believes in seizing the right moment. And to-night struck him as being the right moment." "What are you talking about?" snarled Harker. "For reasons best known to yourself, Mr. Harker"—he glanced from him to Iris Sala, from whose eyes the strange look of triumph had mysteriously vanished, leaving only fear—deadly, gripping fear—"you wished to get rid of your wife." "It’s a lie!" Paul Harker sprang forward, his fist raised to strike. "You will doubtless have ample opportunity for proving it," continued Billy, imperturbably. "By a happy combination of circumstances, a suitable moment—the darkness of a séance—and a suitable motive—robbery—presented themselves to your hand. Acting according to your tradition, you took them. And as far as I can see, Mr. Harker, you would have been successful had you also selected a suitable person. Therein lay your one error." "Am I to understand," said Harker, in a grating voice, "that you are accusing me—of murdering my wife? Why—you miserable cur——" He stopped, choking with anger. "I make no such accusation," answered Billy. "All I state is that I didn’t." He turned gravely to the doctor. "What was the cause of Mrs. Harker’s death?" "Heart failure—caused by partial strangulation with the hand." "Which hand?" The doctor looked at him quickly; then glanced once more at the dead woman. "The right hand." "You swear to that?" "Undoubtedly I swear to it," said the doctor. For the first time Billy Merton withdrew his right hand from his pocket, and held it out in front of him. "The one mistake," he said, grimly. _The first, second, and third fingers were missing!_ For a moment there was a deathly silence; then the doctor suddenly sprang forward. "Stop him!" he roared. But Paul Harker had already joined the woman he had foully killed, and in the air there hung the faint smell of burnt almonds. Prussia acid is quick.