"We are going to kill you painlessly, Poltavo," he said. "It was your life or ours. We do not desire to cause you unnecessary suffering, but here is the end of the adventure for you, my friend." "You are not going to electrocute me?" croaked the man in the chair, in a hoarse cracked voice. "Don't say that you are going to electrocute me, Farrington! It is diabolical, it is terrible. Give me a chance of life! Give me a pistol, give me a knife, but fight me fair. Treat me as you will; hand me to the police, anything but this; for God's sake, Farrington, don't do this!" The doctor reached down and lifted a leather helmet from the floor and placed it gently over the doomed man's head. "Don't do it, Farrington." Poltavo's muffled voice came painfully from behind the leather screen. "Don't! I swear I will not betray you." Farrington made a little signal and the doctor walked to the wall and placed his hand upon a black switch. "I will not betray you," said the man in the chair in hollow tones. "Give me a chance. I will not tell them anything that you----" He did not speak again, for the black switch had been pressed down and death came with merciful swiftness. They stood watching the figure. A slight quivering of the hands and then Farrington nodded and the doctor turned the switch over again. Rapidly they unfastened the straps, and the limp thing which was once human, with a brain to think and a capacity for life and love, slipped out of the chair in an inanimate heap upon the ground. So passed Ernesto Poltavo, an adventurer and a villain, in the prime of his life. Farrington looked down upon the body with sombre eyes and shrugged his shoulders. He had opened his mouth to speak and Fall had walked to the switchboard and was about to put the deadly apparatus out of gear, when a sharp voice made them both turn. "Hands up!" it said. The stone door, through which Poltavo had passed to his doom from the corridor without, was wide open, and in the doorway stood T. B. and a little behind him Ela, and in T. B.'s hand was a pistol. CHAPTER XX T. B. Smith's inspection of the Secret House had yielded nothing satisfactory; he had not expected that it would; he was perfectly satisfied that the keen, shrewd brains which dominated the menage would remove any trace there was of foul play. "Where now?" asked Ela, as they turned out of the house. "Back to Moor Cottage," said T. B., climbing into the car. "I am certain that we are on the verge of our big discovery. There is a way out of the cottage by some underground chamber, a way by which first Lady Constance and then Poltavo were smuggled, and if it is necessary I am going to smash every panel in those two ground floor rooms, but I will find the way in to Mr. Farrington's mystery house." For half an hour the two men were engaged in the room from which Poltavo had been taken. They probed with centre bits and gimlets into every portion of the room.