The Love Boat (1977) : 4x5

Famed author Brian Mallory gives three people free tickets to a Caribbean cruise. He then presents each of them--and Gopher--with gold coins. He explains that they are among the last people to have spent time with his nephew; and offers them $100,000 if they can track down the young man, who is believed to be on one of the islands the ship will be visiting. One of the passengers taking part in the quest is about to donate a kidney to his brother. A young woman follows him around and seems to take a special interest in everything he does. Mallory's wife finally grows tired of his aloof and cruel behavior toward her. She leaves him, and seeks comfort with Doc. An old friend asks Capt. Stubing to leave the ship to help him run his business. A jealous woman accuses Julie of trying to steal her fiancé, a man who was a casual acquaintance of Julie's in college.