Mankind had, throughout its existence, poked and probed into the recesses of nature, trying to figure out how things worked. If one man didn't discover fire, or the use of the lever, or gunpowder, or the atom bomb, or immortality, another would. Man willed to know all nature's secrets, and there was no way of keeping them hidden. Armed with this bleak but comforting philosophy, Dennison packed his formulas and proofs into a briefcase, slipped a two-ounce bottle of the product into a jacket pocket, and left his Riverdale laboratory. It was already evening. He planned to spend the night in a good midtown hotel, see a movie, and proceed to the Patent Office in Washington the following day. On the subway, Dennison was absorbed in a newspaper. He was barely conscious of the men sitting on either side of him. He became aware of them only when the man on his right poked him firmly in the ribs. Dennison glanced over and saw the snub nose of a small automatic, concealed from the rest of the car by a newspaper, resting against his side. "What is this?" Dennison asked. "Hand it over," the man said. Dennison was stunned. How could anyone have known about his discovery? And how could they dare try to rob him in a public subway car? Then he realized that they were probably just after his money. "I don't have much on me," Dennison said hoarsely, reaching for his wallet. The man on his left leaned over and slapped the briefcase. "Not money," he said. "The immortality stuff." * * * * * In some unaccountable fashion, they knew. What if he refused to give up his briefcase? Would they dare fire the automatic in the subway? It was a very small caliber weapon. Its noise might not even be heard above the subway's roar. And probably they felt justified in taking the risk for a prize as great as the one Dennison carried. He looked at them quickly. They were mild-looking men, quietly, almost somberly dressed. Something about their clothing jogged Dennison's memory unpleasantly, but he didn't have time to place the recollection. The automatic was digging painfully into his ribs. The subway was coming to a station. Dennison glanced at the man on his left and caught the glint of light on a tiny hypodermic. Many inventors, involved only in their own thoughts, are slow of reaction. But Dennison had been a gunnery officer in the Navy and had seen his share of action. He was damned if he was going to give up his invention so easily. He jumped from his seat and the hypo passed through the sleeve of his coat, just missing his arm. He swung the briefcase at the man with the automatic, catching him across the forehead with the metal edge. As the doors opened, he ran past a popeyed subway guard, up the stairs and into the street. The two men followed, one of them streaming blood from his forehead. Dennison ran, looking wildly around for a policeman. The men behind him were screaming, "Stop, thief! Police! Police! Stop that man!"