On board his wealthy father's tanker ship, Nick Kegan (Jeff Bridges) leaves a message for his lover, Yvette Malone (Belinda Bauer), on her answering machine. Suddenly, a family associate named Keifetz (Richard Boone) makes a dramatic entrance via helicopter, bringing along a bandaged man, Arthur Fletcher (Joe Spinell). Inside the ship's medical office, Fletcher, while being attended to, confesses a chilling secret: he assassinated Nick's half-brother, the President of the United States, nearly two decades ago on February 22, 1960, in Philadelphia. He recounts how he was hired by a man named Casper, Jr., alongside another gunman, and hid the murder weapon in Room 903 of the Engleson Building. Fletcher seeks to reveal the truth about the assassination to clear his name before passing away, leaving Nick desperate for answers.
Intrigued and seeking justice, Nick travels to Philadelphia, where he discovers the rifle. Just as Nick and his companions plan their next steps, tragedy strikes: a young woman on a bicycle with a child inadvertently witnesses the chaos, leading to the untimely deaths of Nick's friends at the hands of an unseen sniper. Frantically, Nick attempts to alert his father, Pa Kegan (John Huston), but instead reaches John Cerruti (Anthony Perkins), who claims to send assistance. However, their plans are thwarted when the vehicle containing the rifle goes missing.
Eventually, Nick finds himself at his father's lavish estate, where he reconnects with family members, including his troubled mother, Emma (Dorothy Malone). Despite the familial affection, there's conflict as Pa rebukes Nick for abandoning his duties. The tension escalates when Pa concocts a scheme to dismantle the assassination conspiracy.
A turning point emerges when Nick meets Z.K. Dawson (Sterling Hayden), a powerful former political rival who attempts to distance himself from the crime, laying blame on the Philadelphia Police Department, particularly Captain Heller (Brad Dexter) and his ally, Ray Doty (Michael Thomas). Subsequently, Nick learns that he has lost all witnesses to Fletcher's confession, as they either die or disappear under mysterious circumstances.
Later on, Nick's investigation leads him to Joe Diamond (Eli Wallach), a nightclub owner with connections to the assassination. Doty's flashbacks reveal that the crime was orchestrated by the mafia, with Diamond facilitating the grisly details. As Nick's pursuit deepens, he rekindles his relationship with Yvette, but their intimacy is marred by suspicions and emotional turmoil.
As the saga unfolds, Nick discovers Yvette's untruths regarding her employment and learns that deception runs rampant in his family’s dealings. Amid shocking revelations and murderous plots, Nick confronts the realities that his father, Pa, may be behind the assassination. In a dramatic climax, a confrontation leads to chaos, forcing Nick to grapple with shocking family betrayals and the weight of legacy.
Ultimately, forced to make painful decisions, Nick witnesses the tragic demise of his father, who, in a final act of defiance, tumbles to his death, leaving a haunting message as he falls: "put my money in South America!". The emotional weight of familial connections remains heavy, even as Nick struggles to escape the shadows of his family. The story culminates with him calling Yvette's answering machine one last time, clinging to the remnants of their love amid the darkness.
