The episode begins with Jessica's niece Pamela Crane having a dream where she relives her husband Johnny's suicide. She awakens from the dream in the mental hospital where she has been staying. Her father comes the next morning to pick her up from the hospital and send her on a two-week cruise with Jessica. Before they go, Pamela's father Marshall asks another passenger named Andrea Reed to take a picture of the three of them. She agrees, but tells him she is a horrible photographer.
After boarding the boat, a young man bumps into Pamela. He apologizes profusely, then walks away. Jessica goes to cash some traveler's checks, and the woman there tells her that the ship is only 90% booked. She also tells Jessica that they were taking passengers all the way up to the day before.
Jessica meets Pamela back at her cabin, and Pamela is crying when she arrives. They talk about Johnny, and Pamela tells her that he was adopted. Pamela insists that Jessica read Johnny's letter, but as she starts to read, there is a knock at the door. It's a man named Ramon, and he delivers a bottle of champagne with a note that says, "Bon voyage, Pepper." Pamela gets upset because she says that was a pet name Johnny had for her, and no one else ever called her that.
At dinner that night, George Reed and his wife Andrea come over to meet Jessica and Pamela. After they walk away, Pamela looks at the menu. She gets very upset and says that the special that night is Johnny's favorite meal. It is a recipe she made up herself. She walks out of the dining room. Jessica asks the host about it, and he tells her that it is not a part of the menu.
Jessica goes to talk to Diane Shelley, the woman who previously cashed her traveler's checks. Diane gives Jessica the order slip for the champagne, telling her that whoever ordered the champagne paid cash and did not sign the order. Jessica compares the handwriting on Johnny's suicide note to the handwriting on the order, and they appear to match.
Pamela goes out that night to sit on the deck. While she is sitting there, she hears a voice whispering, "Pepper." She goes up the deck stairs towards where the sound seems to be coming from. Not long after, Jessica comes looking for her. She is at the bottom of the stairs with a big cut on her head. She is taken to the ship infirmary where the captain of the ship questions her. She tells him that someone pushed her down the stairs. Jessica arranges for Pamela to spend the night there, then asks to speak privately with the captain. She tells him about the other incidents. She says that whoever is responsible must have booked their trip after Jessica and Pamela. The captain gets a list of people who booked after them, and there are about a dozen names on it. Jessica requests 24-hour protection for Pamela, which the captain agrees to.
Jessica goes for a walk on the deck with Pamela, who tells Jessica that Johnny's real mother wrote to him shortly before Johnny died. She asked him to meet her somewhere, but when he went, she wasn't there. Jessica asks if Pamela ever met her or heard her name, and she says no. Then the man who ran into Pamela when they boarded the boat approaches them. He introduces himself as Russell Tompkins. Jessica invites him to join her and Pamela on their stroll, and he agrees. Then Jessica pretends she has somewhere to be and takes off, leaving the two of them alone.
Jessica calls her brother Marshall and tells him he needs to find out the name of Johnny's mother and her current whereabouts. He says he will call a friend of his who is a judge and see what he can do. Then he adds that Pamela's house was broken into a few days before. Jessica asks about the recipe, then gets off the phone with him. Jessica and the captain talk about the list of suspects and, guessing at how old Johnny's mother must be, narrow the list to three people. The two loud women who almost missed the boat and Andrea Reed. The captain says he has known Andrea Reed for years, and he can't believe it could be her. He also adds that Diane Shelley is also around the right age. A few days earlier, the regular staff member that was supposed to go got sick, and Diane insisted on taking his place.
Meanwhile, Pam and Russell are getting to know each other, in spite of Pamela's insistence that she doesn't want Jessica fixing her up on this trip. He tells her that he is divorced.
Jessica gets the pictures back from the developer. Just then, a message comes across the P.A. system calling "Pepper Crane" to the purser's office. She rushes into the office, where Diane says she received a telegram for her. It says, "Till death do us part. Johnny."
The captain and Jessica talk to Diane, who explains she took the job only because she was trying to escape a bad relationship. One of the ship's stewards comes in and says that the two secretaries, Phoebe and Carla, are in the dining room, but he could not find Mrs. Reed. Jessica goes to talk to them. She says she thinks the cruise is horrible, and she attributes it to the fact that they call this ship "The Jinx Ship." They tell her that they took the trip at the last minute because their company told them that they couldn't save vacation time anymore.
Just then, George Reed walks up to the table. Jessica excuses herself and asks him where his wife is. He says she's in their cabin, but Jessica tells him that someone checked, and she wasn't there. They rush back to the room, where they find her dead with an empty pill bottle by her hand.
Jessica takes George back to her cabin. she tells the captain that they found a lot of pictures of Johnny and Pamela, all of which were taken with a telephoto lens. George Reed says that he doesn't know anything about Johnny. He tells the captain and Jessica that his wife heard the page asking her to come to the captain's office, and she became very agitated.
Jessica gets a call from Marshall, who tells her that Andrea was Johnny Crane's mother. Jessica goes to speak to Mr. Reed and says that once they find the private detective who took the photos and confirm the details, the whole thing will get wrapped up. George insists that his wife took the pictures himself and that she was an expert photographer.
Jessica tells Pamela that Andrea Reed was Johnny's natural mother, but she was not murdered. She speaks to the captain about detaining George Reed, but he refuses to do it because he is not convinced.
In his cabin, George Reed toasts his wife's picture and talks about all the wealth she left him. Jessica shows up at his door, pretending to be very drunk. She tells him that she knows he killed his wife. She shows him the picture that Andrea took of them at dockside, and it is off-center and their heads are cut off. She tells him that she's going to show it to the police and the captain, then stumbles away.
George follows her onto the deck and sees her stumbling around at the bottom of the stairs. When he gets there, however, it is actually Officer Morley. He flips Reed over and Pamela takes a picture of him. He is arrested the next day when they dock.
The captain tells Jessica that George Reed admitted killing his wife. He had planned the murder for a long time, hoping to inherit his wife's fortune. The captain apologizes and invites her to dinner.