As the capsule hurtles toward its intended target, a solitary figure emerges from the icy expanse of the Arctic, guided by a haunting homing signal that disrupts the frozen stillness. In the background, a second observer lurks, their presence as ephemeral as the auroras illuminating the night sky.

Commander James Ferraday, the captain of the USS Tigerfish, receives a critical command from Admiral Garvey: to execute a bold rescue mission aimed at retrieving individuals from Drift Ice Station Zebra, a British scientific weather station dangerously adrift near treacherous ice. However, this rescue operation serves as a facade for a more covert agenda.

As the submarine docks in Holy Loch, Scotland, British intelligence agent Mr. Jones teams up with Ferraday’s crew, alongside an elite U.S. Marine platoon. Once underway, they witness the swift departure of Captain Anders, a stern officer who takes charge of the Marines, as well as Boris Vaslov, a Russian defector whose true loyalties remain enigmatic. The Tigerfish bravely navigates through the ice-laden Arctic, but soon finds its conning tower unable to surmount the thick drift.

Resistance greets Ferraday’s orders when he initiates a torpedo launch to break through the icy surface. Yet, disaster looms when the inner hatch opens, letting seawater flood in and endangering the submarine’s existence. A frantic pumping operation on board averts catastrophe at the last moment. As the investigation unfolds, Ferraday uncovers signs of sabotage—mystifyingly pointing to either Vaslov or Anders.

When the Tigerfish finally breaches the ice, it finds itself in the midst of a blizzard that blots out visibility. Ferraday, alongside Vaslov, Mr. Jones, and the Marines, must bravely trek through the fierce frozen wasteland, motivated by the urgent need to reach Drift Ice Station Zebra. Upon arrival, they discover the research base in shambles, with the scientists barely clinging to life. As Jones and Vaslov interrogate the survivors about the harrowing events, the truth begins to slowly unravel, entangling them in a web of intrigue.

In a pivotal moment, Jones reveals a startling fact to Ferraday, intensifying their mission for a revolutionary British camera, designed to utilize an advanced film developed by Americans. This technology, however, fell into Soviet hands, integrated into a state-of-the-art satellite capable of capturing sensitive images of American missile locations while documenting Soviet sites. Following a malfunction, the satellite disintegrated, scattering its remnants across the Arctic landscape near Ice Station Zebra. The pursuit of the film capsule by both Soviet and British agents escalated into a dangerous confrontation, trapping the scientists in the middle.

Ferraday dispatches his team to search for the elusive canister. During the chaos, Jones discovers an extra tracking device, only to be blindsided by Vaslov, who reveals himself to be a double agent intent on sabotaging their efforts. A fierce confrontation between Anders and Vaslov ensues, at which point a dazed Jones regains consciousness just in time to intervene, tragically wounding his own captain.

As the alert Tigerfish picks up on the signal of advancing Soviet aircraft, Ferraday decides to let Vaslov use the tracker to pinpoint the capsule submerged in ice. Suddenly, a horde of Soviet paratroopers descends, demanding the surrender of the film. In a shocking twist, Ferraday hands over an empty container, setting off a brief but intense firefight once the ruse is discovered. Amid the turmoil, Vaslov tries to seize the film, but Jones manages to injury him. As tensions spiral, Ferraday orders Vaslov to surrender the canister to the Soviets. Before disaster strikes, he activates a detonator, ensuring that neither side can exploit the other’s missile information.

In an unexpected resolution, the Soviet colonel acknowledges that both factions have met their aims, effectively wrapping up their hostile encounter. With the Tigerfish completing the rescue of the civilians, a teletype machine broadcasts an announcement that the “humanitarian mission” has notably enhanced cooperation between the West and the Soviet Union, representing a significant milestone in fragile international relations.