The year is 1964, and the aftermath of a catastrophic nuclear war has left the northern hemisphere devastated. The USS Sawfish, an American nuclear submarine, now sails the vast expanse of the mid-Pacific, making its way toward the seemingly untouched shores of Australia. Commodore Dwight Towers, portrayed by Gregory Peck, and his crew live in a state of suspended existence, each day marked by the creeping threat of radioactive winds from the North that promise to obliterate all life as they know it.
As they dock at the port of Melbourne, the Australian Government and the scientific community express hope that life might still persist in the Southern Hemisphere or even in Antarctica. They task Towers and his crew with a risky mission: to journey north and investigate both radiation levels and a mysterious Morse code signal that originates from around San Diego, California. Given this delicate assignment, Towers is joined by an Australian ensign, Peter Holmes, played by Anthony Perkins, who acts as a liaison officer for the perilous expedition.
In a moment steeped in compassion, Peter and his wife Mary, illustrated by Donna Anderson, throw a gathering to elevate Towers' spirits, acknowledging the heavy loss he has faced. To distract Towers from his melancholic thoughts, they invite Moira Davidson, brought to life by Ava Gardner. As opposed to confronting the futility that surrounds them, the night offers a breath of fresh air, igniting an unexpected romance between Towers and Moira. However, the specter of his lost family in Connecticut looms heavily over Towers, creating an inner turmoil that leaves him confused. He even mistakenly envisions Moira as his deceased wife, Sharon. Though Moira offers to fill Sharon’s role—out of her own loneliness and fear—Towers steadfastly rejects this notion and departs on his mission without informing her of his plans. Moira's cousin, Julian Osborn, whose character is played by Fred Astaire, reveals to her about Towers' journey, deepening her concern for the man they've come to care about.
The Sawfish's first stop is Point Barrow, Alaska, where the crew is met with harrowing news: radiation levels are rising. Their next destination is the eerily silent streets of San Francisco, where one crew member, yeoman Ralph Swain, portrayed by John Meillon, is so overcome with desperation that he chooses to desert the sub in favor of facing his demise back home. Aware of the risks involved, Captain Towers sympathetically bids farewell to Swain, who embodies the haunting reality of preferring the familiarity of home over the ominous uncertainties of the future.
Continuing further south towards San Diego, Lt. Sunderstrom, played by Harp McGuire, bravely ventures onto land, cloaked in a full radiological suit. Tasked to uncover the source of the signal, he learns the signals nobody sent; a random series of Morse code clicks produced by a broken window shade and a Coca-Cola bottle. Racing against time, he manages to inform the sub of his findings before it becomes too late.
With their destinies intertwined and a heart-wrenching sense of resignation, the Sawfish returns to Melbourne. Here, Towers reunites with Moira at her father’s farm, and amidst fleeting moments of joy, he receives the grim news that the deadly winds have reached Brisbane, escalating his sense of duty and urgency. As a fitting witness to impending tragedies, the two attend the Australian Grand Prix, where Julian bravely pursues his dreams, only to succumb to the chaotic nature of fate.
The two then embark on a long-awaited fishing trip, capturing a fleeting moment of joy amidst their ticking clock. Their romance blooms in the shadow of the world’s end as they escape to the quiet refuge of an inn, where laughter mingles with the haunting echoes of a world at its twilight. Laughter and music blur with sorrow as they relish their last tether to life.
From this short-lived escape, stark reality crashes in when news arrives that one of Towers' crew, Seaman Ackerman, has just developed symptoms of radiation poisoning. The winds of despair spiral into action, and Towers is faced with agonizing decisions about his crew’s fate, as well as his own attachment to Moira. The crew grapples with the idea of returning to their homes, while Moira’s friendship with Peter takes a tragic turn; Mary descends into despair, recognizing the futility of their situation.
In a desperate moment of clarity, Towers acknowledges the time left is running short and learns that Moira is racing towards him, desperate for a final connection. Their goodbye is bittersweet, as Towers expresses his love but must return to his responsibilities aboard the Sawfish. As the submarine embarks on its final journey, Moira speeds along the coastline, hoping for one last glimpse of Towers as he descends into the depths of the ocean.
The film closes on haunting images of an abandoned, wind-swept Melbourne, evoking a great vacuum left by humanity's extinction. The once vibrant city, now entirely desolate, holds echoes of voices long silenced. The final scene rises majestically over a backdrop of poignant music, showcasing the poignant banner from a previous Salvation Army meeting: "There is still time...Brother."
