Queenie Sorenson [Natalie Schafer] frets to her husband, Osbert Sorenson [Cecil Kellaway] about calling the police after a sobbing voice drifts from the next room. The pair glance at Eloise Crandall [Judith Evelyn] as she staggers through the living area, muttering apologies for Drummy [Jeff Chandler] before she bursts onto the patio and screams his name. Her sudden presence ends with a fatal fall onto the sand, her body left behind with a broken glass nearby, seen only from the edge of the frame.
The following day, officers study the scene—glass shattered on the beach and a boat moored at the dock adjacent to the house. A blonde woman is seen removing clothes from the railing, while a doorbell rings and Lynn Markham [Joan Crawford] enters, greeted by Amy Rawlinson [Jan Sterling], who introduces herself as the real estate agent. Amy explains the previous tenant, Eloise Crandall, left abruptly the night before and paints her as a quiet, respectable former tenant. Lynn tours the house, noting the boat’s proximity and asking Amy to arrange for its removal, then questions who would profit from the malevolence around the property. The police presence outside, including a measured coldness toward the crime scene, hints at a larger mystery.
Lt. Galley [Charles Drake], the port police officer, visits Lynn on the patio and shares a flood of details about Eloise’s life—her engagement to a gambler, a recent marriage, and a desire for solitude. He teases the possibility of a suicide but suggests there may be more beneath the surface, especially given Eloise’s ties to the Sorenson family. The Sorensons themselves watch from a distance, urging Drummy to rekindle a connection with Lynn, hoping to secure a new arrangement that would keep the money flowing in their favor.
The next morning, the sound of a revving boat wakes Lynn, who finds Drummy [Jeff Chandler] preparing breakfast and moving about the house. He probes for access to Lynn and mentions a visit to a nearby island, but she remains unimpressed. A new officer, Frankovitch [Stuart Randall], arrives with questions about the clothing belonging to the dead woman, provoking Drummy to finally release the key to a neighboring door. On the beach, the Sorensons gossip about their money and the possibility of profiting from Eloise’s death, suggesting Drummy could be introduced to a new beneficiary who could “pass away as conveniently as Eloise did.”
That afternoon, Drummy is seen flirting with Lynn again, who rebukes his advances and returns home to hear of a prospective buyer. Amy arrives with a potential deal, asking for the key so the sale can proceed, and Lynn insists the boat be relocated and the railing repaired. Later, Amy takes Drummy for a ride on her boat after paying him, accusing him of losing interest after Eloise’s death; he retorts with a hard line about women, hinting at a dangerous past. A distinctive Y-shaped scar appears behind Drummy’s ear, a detail Lynn notices when he bores into her with a predatory charm.
That night, Lynn uncovers Eloise Crandall’s diary hidden in a secret cutout behind the fireplace. The diary details Eloise’s generous help to Drummy, the gambling debts tied to the Sorensons, and Drummy’s abrupt withdrawal from Eloise’s life. Eloise had pleaded with Drummy to join her in Los Angeles, while accusing him of exploiting her money, and her last entry hints at an oscillation between love and fear. Lynn tosses the diary into the fire, only for Drummy to appear in a suit, insisting they have a date. The tension escalates as the Sorensons intrude, and Lynn makes it clear they are not welcome; Drummy asserts his interest and kisses her, while Lynn tests his sincerity with the diary’s revelations.
The morning after, Lynn discovers a suspicious absence—Drummy’s boat is gone—and Mrs. Murchison [Marjorie Bennett], the cleaning woman, is at the house with a small gift of cufflinks and a tie. The Sorensons press Drummy to renew his alliance with Lynn, pressing for a bet on her money as a security for a life together. Lynn, unsettled by the growing danger, begins to drink and smoke while waiting for a call that never comes. Drummy and Lynn exchange glances across the yard as the police keep a watchful eye, debating whether to arrest him, but choosing to delay.
Weeks pass in a tense balancing act: the couple share quiet moments on the dock, where Drummy recounts a painful childhood, the scar behind his ear, and the truth about his mother’s suicide. He reveals that his aunt and uncle—who raised him—wanted him to marry Lynn for her fortune, while he confesses his genuine feelings for her. Amy, observing this from the sidelines, warns Lynn that Drummy may be playing her for money, and she hints at a possible motive: Amy herself has designs on Drummy and has even tampered with the boat’s fuel pump.
As a storm gathers, Lt. Gulley and Frankovitch confront the possibility that Amy orchestrated Eloise’s death and manipulated information to keep Drummy’s affections away from Lynn. The couple’s plans for Catalina on the boat become a symbol of their tentative future together, but Lynn’s suspicions intensify as she discovers a concealed fuel pump and remembers Drummy’s warning that the vessel could ignite. A tense moment on the beach ends with Lynn realizing Drummy’s manipulation, and she resolves to act to protect herself.
Amy is eventually confronted by the law as the truth about Eloise’s murder—disguised by a web of extortion and romance—comes to light. In a climactic confrontation, Lt. Gulley detains Amy and explains that Lynn’s life was spared by Drummy’s intervention, though the danger remains palpable. Drummy and Lynn, battered but hopeful, share a final kiss as the sun returns and the cheerful score lifts the moment, signaling a fragile but renewed bond between them as they prepare to leave behind the shadow of the past.
