On a one-week Mediterranean pleasure cruise aboard the yacht of movie producer Clinton Greene, the guests include actress Alice Wood; her talent-manager husband Anthony Wood; talent agent Christine; screenwriter Tom Parkman and his wife Lee; and director Philip Dexter. All but [Lee] were together at Clinton's home one year before, on the night a hit-and-run accident resulted in the death of Clinton's wife, gossip columnist Sheila Greene.
Greene, a parlor game enthusiast, informs everyone that the week's entertainment will consist of “The Sheila Greene Memorial Gossip Game.” Each guest is assigned an index card containing a secret that must be kept hidden from the others. The object of the game is to uncover everyone else’s secret while protecting your own. Each night, the yacht anchors at a different Mediterranean port city, where one of the six secrets is revealed to the entire group. The guests receive a clue, then head ashore to search for proof of who holds the card bearing that secret. The game for that night ends when the actual holder discovers the proof.
From the outset, suspicion grows that the so-called “secret” cards might reflect real past truths. On the first day, the card read, “YOU are a SHOPLIFTER,” and it is assigned to [Philip Dexter], yet it seems to apply to [Alice Wood], who was caught shoplifting before achieving fame.
On day two, Christine narrowly escapes danger when someone turns on the boat’s propellers while she is swimming near the vessel. The second secret is soon disclosed: “YOU are a HOMOSEXUAL.” In the evening, Greene travels to the chosen island to stage the next round, arriving at a monastery where the guests are dressed in hooded robes. Greene also disguises himself as [Alice Wood], wearing a wig and makeup. The ritual does not flow as smoothly as the first night, and tensions begin to rise.
The following day, discussion aboard the yacht centers on the game’s oddities as Greene fails to return. Returning to the monastery, the guests discover his corpse.
Back on the yacht, [Tom Parkman] suggests that Greene was murdered by one of them and proposes that the rest lay their cards on the table. Five cards are revealed: “YOU are a SHOPLIFTER,” “HOMOSEXUAL,” “EX-CONVICT,” “INFORMER,” and “LITTLE CHILD MOLESTER.” The “HOMOSEXUAL” card clearly points to [Tom Parkman], who had a former connection with Greene before his marriage to [Lee]. Parkman reveals that he had a sixth card, “YOU are a HIT-AND-RUN KILLER,” and suggests that the hit-and-run killer was the one who silenced Sheila’s death cover-up.
Christine explains that, during the Second Red Scare, she once informed on left-leaning actors to advance her career and gain agency, and now tries to help them find work out of guilt. Anthony discloses that he is the “EX-CONVICT.” Dexter is revealed to be the “CHILD MOLESTER.” [Lee], who has been drinking heavily, tearfully confesses to having killed Sheila while driving drunk the year before, and to killing Clinton the previous night after he provoked her with this knowledge. Distraught, she locks herself in her cabin and is later found dead, wrists slit, in the bathtub of Greene’s cabin, sealing the mystery momentarily.
On the final night, the crew and most guests travel ashore to a party, while Dexter remains on the ship, lacking funds. Parkman, watching from the vessel, notices lights blinking on and off and returns to find Dexter pondering unresolved elements of earlier events. Dexter suspects that [Lee] “killed” a dead body and that the real killer rearranged the scene to frame her. Parkman then notices that the six secrets spell out the name SHEILA, with the final letter missing; the pattern’s completion hinges on the missing “A.”
Having previously learned the game’s actual purpose, Parkman secretly swaps his own card—now reading “YOU are an ALCOHOLIC” (the missing A)—for the harsher “YOU are a HIT-AND-RUN KILLER,” exploiting the fact that both secrets apply to [Lee]. He later engineers Lee’s realization that the game was designed to expose her role in Sheila’s death. On the second night, Parkman murders Greene and frames [Lee] for the crime. He secretes sleeping pills into her bourbon, carries her body to the bathtub, and slits her wrists, making the death appear as suicide. With Lee’s estate valued at about $5 million, Parkman becomes wealthy and free to end his marriage that had bored him.
Dexter’s attempt to kill Greene with the boat’s propellers is part of his own bid to keep secrets hidden. Parkman confronts Dexter, but is interrupted by Christine, who had come aboard for a clandestine encounter and has overheard the entire exchange. In the end, Dexter and Christine seize leverage over Parkman: as a condition for concealing the truth about Greene’s death, Parkman must finance their next film using the fortune from Lee’s estate.
The cruise concludes with a tangled web of motives, deceit, and revenge, where the elaborate game of secrets unravels the lives of everyone aboard, exposing how far some will go to protect their darkest acts—and how a single, orchestrated scheme can collapse the fragile threads of trust that bind a group together.
