J.P. Tannen Jon Voight is a former professional golfer living in California, estranged from his three children who reside in New York with their mother, Kathleen Millie Perkins, and their stepfather, Mitchell Richard Crenna. Hoping to reconnect, Tannen decides to take them on a Mediterranean cruise, aiming to show Kathleen that he has changed, though she remains unconvinced.
On the ship, Tannen is often distracted by the prospect of meeting women, including Marie-Christine Barrault, a French archaeologist. He frequently leaves the children to entertain themselves and even reserves a table for five in the dining room, secretly hoping to lure an adult female companion for the fifth seat.
His youngest son, Truman-Paul Robby Kiger, has a learning disability, which Tannen pushes himself to help him overcome, though with impatience. Their adopted oldest son, Trung Son Hoang Bui, is caught stealing food from the ship's galley and trying to order drinks with a fake ID. Their sister, Tilde Roxana Zal, is sensible and perceptive but still too young to fill a parental role for her brothers.
Tannen begins to feel inadequate as a father, sometimes inviting his children to think of him as a "friend" and even encouraging them to call him "J.P." The first port, Rome, offers a temporary thaw as a family enjoys time together and Marie is impressed by his patient, caring interactions with the kids.
En route to Athens, tragedy strikes: Kathleen is killed in a car crash in New York while taking the family's dog to the vet. Grief-stricken, Tannen meets the children's stepfather, Mitchell, in Athens. He explains that the burial has already taken place and that he has flown to Europe to escort the children home for a memorial service later. Tannen insists on telling the children the news himself and asks for more time, while Mitchell reluctantly agrees to let the children remain aboard for a while longer.
As the ship sails to Cairo, Tannen confides the truth about his limited time with the kids to Marie. He then joins the family on a trip to the Pyramids, where he finally breaks the devastating news to the children about their mother's death, leaving them reeling with grief.
At Tunis, Trung runs away, seeking a way back to the United States by sea. Tilde reveals Trung's history of running away, a fact that had escaped his notice. A chase ends with them finding him in a marketplace, and Trung tells his father he needs him as a father, not as a friend.
Mitchell awaits in Genoa, prepared to take the children back to the United States. In a turning moment, Tannen gently informs Mitchell that he will keep the children, and then he lists the children's friends and teachers, demonstrating a renewed commitment to being part of their lives and proving he will be present for them going forward.
