An unknown aircraft approaches North America from Europe. American bombers of the Strategic Air Command are scrambled to meet the potential threat. As a fail-safe protection, the bombers have standard orders not to proceed past a certain point without receiving a special attack code. However, due to a technical failure, the attack code is actually transmitted to Group Six, consisting of six Vindicator supersonic bombers, and they advance past their fail-safe point on the way to attack Moscow. Meanwhile the original "threat" is proved innocuous and recall orders are issued, but Soviet jamming prevents the bombers from hearing them.
At meetings in Omaha, the Pentagon, and in the fallout shelter of the White House, American politicians and scholars debate the implications of the attack. Professor Groteschele (played by Walter Matthau in the 1964 movie), who is loosely based on Henry Kissinger, suggests the United States follow this accidental attack with a full-scale attack to force the Soviets to surrender.
The American President contacts the Soviet premier (unnamed in the movie, but who the book names as Nikita Khrushchev) and offers assistance in attacking the group. The Soviets decline at first.
At SAC headquarters, General Bogan attempts to stop the attack. His executive officer, Colonel Cascio, wants the attack to continue. Cascio attempts to take over command of SAC, but is stopped by Air Police; however, in doing so, he wastes precious time.
The Soviets accept American help in attacking the two surviving bombers of Group Six. However, the Soviet commander, Marshal Nevsky, mistrusts General Bogan enough to attack the bomber carrying decoys, guaranteeing the plane piloted by Colonel Grady will be able to finish the attack.
Colonel Grady contacts SAC to inform them that they are about to make the strike. The Soviets fire a barrage of nuclear-tipped missiles to form a fireball to knock the low-flying Vindicator out of the sky. The President and Grady's wife (son in the made-for-television movie) both try to persuade him that there is no war. Under standing orders that such a late recall attempt must be a Soviet trick, Grady ignores them. The Vindicator's defensive systems operator fires two missiles that decoy the Soviet interceptor missiles to detonate at high altitude. Grady tells his crew that "We're not just walking wounded, we're walking dead men" due to radiation from the burst. He intends to fly the aircraft over Moscow and detonate the bombs in the plane. His copilot notes "There's nothing to go home to."
When it becomes apparent that one bomber will get through Soviet defenses and destroy Moscow, the American President offers to have an American bomber destroy New York at the same time. The Soviets accept.
The 1964 film version was not as successful as it might have been had it not had the misfortune to be released shortly after Dr. Strangelove or: How I Learned to Stop Worrying and Love the Bomb, which shares many obvious plot similarities with Fail-Safe but adds black humour and satire to the mix.
The novel was published in October 1962, at the same time as the Cuban missile crisis, and influenced popular debate on the controls used by the United States on nuclear weapons.
The real command system used by SAC and its successor, Strategic Command, differs vastly from the system portrayed in the movie and is based on the KISS principle--keep it simple, stupid! Multiple single sideband transmitters around the world broadcast coded Emergency Action Messages by voice, not by machine. Submarines at sea are contacted by longwave Morse code signals.