"Our nineteenth failure!" observed Sir Charles Venner, folding his arms and looking down at the corpse with a face of stone. "And they have all died of shock. Nothing else." Mr. Cavanagh started forward. "How can you be sure of that?" he demanded. "How do you know that your accursed solution did not poison him?" The young man's face was the hue of ivory, but his big eyes were ablaze with passion. Sir Charles Venner gave a wintry smile. "We have proved it beyond doubt," he replied. "We have tested the blood a hundred times." "Bah!" retorted Cavanagh with a savage sneer. "A fig for your tests. But even if they are reliable, how do you know that he did not bleed to death from the wound you made in his heart?" "Test again, autopsy. Would you care to see? Look here!" He caught up a knife and approached the corpse. "I'm willing, Cavanagh, to bet you a thousand pounds that not one drop of blood has passed my puncture in the ventricle!" "Done!" "Venner," cried Dr. Fulton, "Venner, you are betting on a certainty." "Then I'll pay the stake I win to any charity you like to name." Sir Charles Venner bent over the body, but even as he poised the knife to cut, Mr. Cavanagh cried out in strangled tones: "Stop! I--I withdraw." Venner looked up with a cold sneering laugh. "Then pay!" said he. "No--no! I--I--can't afford it." Mr. Cavanagh put his right hand into his breast pocket. His countenance was perfectly livid. He stepped back a pace and looked at Marion. "George!" she cried, "what ails you, dear?" She was trembling like a leaf in the wind. "Life!" he answered, and uttered a laugh that still echoes in my ears. Next instant he produced a revolver and before our eyes put the muzzle to his mouth. There followed a click, a sharp report, and he fell at our feet a corpse.