Captain Nolan, portrayed by Richard Harris, is an Irish-Canadian fisherman facing the pressing burden of his boat's mortgage as he attempts to sell marine life caught in the ocean. His crew embarks on a quest to capture a formidable great white shark for a local aquarium, only to find themselves entangled with an orca killer whale, which becomes a central figure in their dangerous journey. When the orca intervenes to kill the shark, it inadvertently saves Ken, played by Robert Carradine, who becomes the target of this vengeful creature.
As the narrative unfolds, Captain Nolan shifts his focus to this newfound adversary: the orca. In a tragic twist, during their efforts to capture what he mistakenly believes to be a male orca, Nolan harpoons a pregnant female instead. The heartbreaking aftermath sees the crew onboard as the female orca miscarries, and the crew, in a moment of detachment, tosses the fetus overboard, provoking the male orca's wrath. In an emotional display of grief and anger, the male orca retaliates, sinking the ship in an attempt to rescue its deceased mate. Amidst the chaos, crew member Novak, played by Keenan Wynn, meets a grisly fate at the hands of the orca, pulled beneath the waves to be devoured.
The following day, the male orca pushes the dead female to shore, prompting Alan Swain, portrayed by Scott Walker, to confront Nolan about the consequences of his actions. Faced with mounting pressure from the villagers—who believe the orca's presence is disrupting local fishing resources—Nolan is urged to eliminate the orca. The tension escalates as the orca terrorizes the village, sinking fishing boats and rupturing fuel lines, leading to a catastrophic fire that threatens the community.
In a significant moment, Dr. Rachel Bedford, played by Charlotte Rampling, a whale expert and colleague of Ken, enlightens Nolan on the similarities between whales and humans. She warns him, > "If he (the orca) is like a human, what he wants isn't necessarily what he should have." Nolan, grappling with his own grief from the loss of his wife and unborn child in a drunk driving incident, confides in Rachel his deep empathy for the orca and vows not to engage in combat with it.
However, when the orca assaults Nolan's seaside home—where his injured crew member Annie, portrayed by Bo Derek, is trapped—Nolan's resolve begins to fade. The orca's brutality leads to Annie suffering a horrific injury, forcing Nolan to confront his initial promise. With only a few crew members left, including Paul, played by Peter Hooten, and the addition of Jacob Umilak, a local with expertise on orcas portrayed by Will Sampson, they embark on a harrowing chase to confront the vengeful beast.
The pursuit culminates at the Strait of Belle Isle, where tragedy strikes again when the orca seizes Ken, devouring him alive. As the crew tirelessly follows the orca, Paul is thrown overboard and drowned during a violent confrontation. In a final, desperate bid, Nolan manages to strike the orca with a harpoon, but the ensuing chaos leads to his own demise. In a heart-wrenching finale, Nolan is separated from Dr. Bedford and ultimately killed by the vengeful whale, slipping beneath the waves in a tragic, cross-like position. As the orca fades into the icy depths, Dr. Bedford is rescued by a helicopter, left to contemplate the devastating cycle of revenge and loss.
