For an hour and a half silence reigned in the cave. A stir was heard outside and Admiral Clay, the President's personal physician, entered leading a stout gray-haired man. Dr. Bird whistled when he saw them and leaped to his feet as another figure followed the admiral. "The President!" gasped Carnes as the officers came to a salute and the marines presented arms. The President nodded to his ex-guard, acknowledged the salute of the rest and turned to Dr. Bird. "Have you met with success, Doctor?" he asked. "I have, Mr. President; or, rather, I hope that I have. At the same time, I would rather experiment on some other victim of their deviltry than the one you have brought me." "My decision that the one I have brought shall be the first to be experimented on, as you term it, is unalterable." * * * * * Dr. Bird bowed and turned to the dwarf who had been a sullen witness of what had gone on. "Slavatsky," he said slowly, "your game is up. I have witnessed one of your brain transfusions and I know the method. I gather from your notes that the menthium you have hidden in that cabinet is still as potent as when it was first extracted from a living brain, but in this case I am going to draw it fresh from one of your gang. Some of the details of the operation are a little hazy to me, but those you will teach me. I am going to restore this man to the condition he was in before you did your devil's work on him and you will direct my movements. Just what is the first step in removing the menthium from a brain?" The dwarf maintained a stubborn silence. "You refuse to answer?" asked the Doctor in feigned surprise. "I thought that you would rather instruct me and have me try the operation first on other men. Since you prefer that I operate on you first, I will be glad to do so." He stepped to the opposite wall and in a few moments had opened the dwarf's hiding place and taken out the flask of menthium. "Carson," he said, "after you had watched Slavatsky inject menthium into Willis, you took lethane and expected him to inject menthium into your brain. Instead of doing so he withdrew a portion from your brain and put it in this flask. I have reason to believe from his secret records which I found in the cabinet with this flask that he has done so regularly. Are you willing to instruct me while I remove the menthium from him?" "The dirty swine!" shouted Carson. "I'll do anything to get even with him, but I have never performed the operation. Only Slavatsky and Willis have operated." "Will you help me, Willis? asked Dr. Bird. "I'll be glad to, Doctor. I am sick of this business anyway. At first, Slavatsky just planned to give us abnormally keen brains, but lately he has been talking of setting himself up as Emperor of the World, and I am sick of it. I think I would have broken with him and told all I know, soon, anyway." "Throw him in that chair," said Dr. Bird. * * * * *