Under microscopic study and chemical analysis, investigators determined that nitro-glycerine had caused the explosion. The fused mass of electronics wreckage in Smith's trailer were identified as parts of a computer assembly. Thousands of dollars had been spent on components over the past three years. Purchases, usually for cash, were traced to various electronic supply companies in the greater Los Angeles area. Dr. Smith's bank account showed a balance of only $263.15. But the big find came from a safety deposit box in the same branch bank. There, along with a birth certificate, his mother's marriage license, an insurance policy, his doctor's degree from the University of Wisconsin and an unused passport, was a duplicate set of computer memory tapes. * * * * * It took the FBI forty-eight hours to play a few selected segments from these tapes, which obviously had been recorded over a period of several years. Two notations made by Agent Cowles indicate the type of material contained on the tapes: "If a deliberate attempt were made to run a thermonuclear test explosion within the frontiers of Russia, in such a way as to avoid detection, it would almost certainly be successful...." "The Soviet Union may soon develop a new ratio of fusion to fission energy in high yield weapons and will require additional data...." FBI agents listening to these playbacks were convinced, almost to a man, that they had stumbled across the hottest espionage trail since the arrest of Klaus Fuchs and the case of the Rosenbergs. A round-the-clock security guard was placed outside the hospital room of John O'Hara Smith, while Federal authorities waited impatiently to see whether he would live or die. Smith would answer, or leave unanswered, a lot of vital questions. * * * * * Security notwithstanding, it was the day after Labor Day before the medical staff of General Hospital would permit the first direct questioning of Dr. Smith. And then the interrogators were instructed: "Only a few minutes." Three men filed quietly into Smith's room as soon as the nurse removed his luncheon tray. They stood in a semi-circle around the foot of his bed. Agent Frank Cowles opened a black leather folder the size of a small billfold and presented his credentials. He introduced General Sanders and Security Officer Busch. It was the first time any of the men had seen John O'Hara Smith. The reports had called him pudgy, but now he had lost twenty pounds and his cheek bones were gaunt under his pallid skin. He wore unusually thick, dark-rimmed glasses that magnified his eyes and gave him an owlish appearance. He returned their scrutiny with a mixture of assurance and impatience, like a professor waiting for his class to come to order. "Good morning, gentlemen," he said tartly. "It's about time someone came to see me about this...." Cowles cleared his throat and suggested cautiously: