A massive collision occurs between a comet and an asteroid dubbed Orpheus, which now heads for Earth on a catastrophic trajectory. This five-mile-wide meteor brings chaos as smaller, swifter fragments fall to the ground, prompting the United States government and military to engage in a web of political posturing. Central to the narrative is Dr. Bradley (Sean Connery), who oversees a covert nuclear missile platform named Hercules, while his Soviet counterpart, Dr. Alexei Dubov (Brian Keith), operates a similar platform known as Peter the Great.
As the situation escalates, President (Henry Fonda) grapples with military advisors who caution against acknowledging Hercules' existence. In a bold move, the President informs the nation about Hercules, portraying it as a visionary response to the imminent threat posed by Orpheus. He extends an olive branch to the Soviets, suggesting they also possess the foresight of such technology.
With the clock ticking, Bradley and Sherwood maneuver to the control center for Hercules, discreetly situated beneath the Sony Building in New York, under the command of Major-General Adlon (Martin Landau). In an effort to ease tensions, Dubov and the eloquent voice of his assistant, Tatiana Donskaya (Natalie Wood), arrive at the facility. Dubov hesitantly agrees to collaborate with Bradley on theoretical strategies, despite the political constraints preventing an acknowledgment of the Soviet's defensive capabilities.
As fragments of the meteor continue to wreak havoc on Earth, the Soviets finally concede the existence of their weapon platform and agree to cooperate. The two platforms, Hercules and Peter the Great, are reoriented to target the meteor. In a stunning turn of events, Peter the Great launches its missiles first, followed by Hercules, but not before a devastating fragment obliterates New York City, reducing iconic structures to ash.
Within the control center, chaos unfolds as workers face impending doom from the East River flooding their makeshift sanctuary. The surviving crew members muster their resolve and escape through the subway, amid urgent broadcasts relaying the news of their success: Orpheus has either been destroyed or redirected harmlessly.
Finally, the scene transitions to an airport adorned with both Soviet and American flags. In this poignant moment, Dubov and Tatiana bid farewell to Bradley and the team, boarding a flight destined for Russia, embodying a glimmer of hope amidst the shared struggle against a common foe.
