Robert Bellamy, an agent of the ONI receives a mission on behalf of NSA: to locate the witnesses of the crash of an experimental meteorological balloon in Switzerland, for which he is only given the date, the place where it happened, and the fact that the witnesses were passengers of a bus tour. He is given an unlimited budget but is told he must work strictly under cover. After he finds the first witness, he discovers that the meteorological balloon was actually an alien spaceship. He tracks the witnesses one by one and reports their names to NSA. Without his knowledge, the names of the witnesses are then communicated to the intelligence organizations of their respective countries, and each of them is assassinated shortly after. These actions are coordinated under the name "Operation Doomsday", under the leadership of a figure known only as Janus.
Robert's personal history is shown through flashbacks: he rose in the military ranks under the mentorship of Admiral Ralph Whittaker, and during a combat flight in Vietnam his plane was taken down, with Whittaker son's dying in the crash and Robert being badly injured. Doctors declare that he has no chance of survival, but a nurse named Susan convinces them to operate on him and encourages him to keep his fighting spirit. He and Susan fall in love after his recovery and marry. Robert is then recruited to become a spy for ONI, but this job takes over his personal life until Susan divorces him and marries a business tycoon named Monte Banks, while Robert isolates himself and dedicates even more to his work.
