The time is the early-to-mid-1960s, the height of the Cold War between the United States and the Soviet Union. An unknown aircraft approaches North America from Europe. American bombers of the Strategic Air Command (SAC) are scrambled to their fail safe points near Russia. The bombers have orders not to proceed past their fail safe points without receiving a special attack code. The original "threat" is proven to be innocuous and recall orders are issued. However, due to a technical failure, the attack code is transmitted to Group Six, which consists of six Vindicator supersonic bombers and four escort fighters. Colonel Grady, the commanding pilot of Group Six, tries to contact SAC headquarters in Omaha, Nebraska to verify the fail-safe order (called Positive Check), but due to Soviet radio jamming, Grady cannot hear Omaha. Concluding that the attack order and the radio jamming could only mean Nuclear warfare, Grady commands Group Six towards Moscow, their intended destination.