A chance encounter with members of an Anti-Nuclear commune leads 30-year old Poul Anders to apply for a position at the San Onofre CA nuclear power plant. The commune's plan calls for Poul to trigger a "small" nuclear explosion that will lead to the closing of all nuclear power plants. Poul's mother died as the result of radiation poisoning, a strong motive for sabotage. But Poul is not a particularly good saboteur. He is easily distracted, by girls for example, and by the work itself. San Onofre traces Poul's gradual penetration of the reactor complex through the initial interview, the security check, the psychiatrist, the simulated alert, the red-badge training sessions, until, with his life finally under control, everything goes wrong.