This unnerving procedural thriller painstakingly details an all-too-plausible nightmare scenario in which a mechanical failure jams the United States military’s chain of command and sends the country hurtling toward nuclear war with the Soviet Union. Working from a contemporary best seller, screenwriter Walter Bernstein and director Sidney Lumet wrench harrowing suspense from the doomsday fears of the Cold War era, making the most of a modest budget and limited sets to create an atmosphere of clammy claustrophobia and astronomically high stakes. Starring Henry Fonda as a coolheaded U.S. president and Walter Matthau as a trigger-happy political theorist, Fail Safe is a long-underappreciated alarm bell of a film, sounding an urgent warning about the deadly logic of mutually assured destruction.