"So you are looking for Professor MacRoberts, a private investigator," Chetzisky chuckled softly. "There is something familiar about you; I should have paid more attention to my suspicions in the beginning. You're someone I met once. That beard confuses me." He waited for me to answer. I had to keep him talking; the paranoiac loves it. All Armstrong's men needed now was time. They were at the doorstep. "I'm Doctor Arnold Bailey of Atlantic University." Chetzisky wrinkled his forehead. "We met about four years ago en route to the St. Louis convention." "Yes," he said slowly as if the recollection was gradually unfolding itself. "Yes, I remember you now. In fact, very well. We had a most interesting chat; do you recall it?" "Something about making the world peaceful, wasn't it?" "That's correct," Chetzisky commented with approval. "It was just my dream then. Now it's real, thanks to the unfortunate Doctor MacRoberts. You saw that incline outside. At its top is a drum filled with crude radioactive ore that MacRoberts discovered. The whole is charged with three milligrams of the new purified radioactive element. It was extremely easy to isolate. A simple precipitation process involving some hot ethyl iodide and a 0.1 Normal solution of cuprous chloride...." He stopped abruptly as he detected a slight forward motion on my part. I threw him a question to dissolve the tension. "What is the name of the new element?" "You must admit it is difficult to call it 'MacRobertium.' Besides, it hasn't the scientific flavor," he said with an amused smile. "The Scots weren't meant for scientists. I call it simply 'MCR'." He motioned me to fall back a few steps and then went on. "The remarkable property of MCR is its diffusion rate, something like two centimeters a minute, assuming a specific gravity of 2.7 for the medium. MacRoberts traced a vein containing MCR ore to this point and for the past two months I've been impregnating it with refined MCR, converting it into a slow, controlled reactor." The Doctor was warmed up now, and I didn't dare interrupt for fear of bringing him out of his paranoic trance. Armstrong might arrive any minute. I hoped. "When the time comes," he continued, "and I believe it is now, I will remove the moderator bar from the drum at the top of the incline and release it. It will strike a trigger mechanism which will catapult it into the face of the vein of MCR ore. The critical mass will be exceeded and a planetary atom bomb will have been born." His eyes were shining now with the madness of his dream. "The chain reaction will proceed through the earth's plastic mantle and down into the liquid core." He paused to enjoy the pleasure of his speculations. "Then within ten hours I calculate the earth will exist no more. It will become a mushrooming cloud of cosmic dust. It deserves no better," he added bitterly; "I tried to give it peace." * * * * *