The episode starts with Lucy reading a book by her nightstand, called the Mockingbird Murder Mystery. She is deeply engrossed in the book, so much that she accidentally dips a cracker in a jar of cold cream. Ricky comes home, happy to announce that the Tropicana wants Ricky to stay on another month. Ricky gets ready for bed, and goes to kiss Lucy, startling her and causing her to throw her book out the window. Lucy asks Ricky to get her book, but he refuses. She begins thinking about possible endings to the book, which Ricky joking suggests the husband. He begins acting out a scenario of how to kill a wife.
The next morning, Lucy gets her book from outside and begins reading it again while cooking breakfast. Ethel comes in and scares here again, her book flies out the window again. Ethel tells Lucy that she can read her fortune, but Lucy doesn't pay any attention to it. Ethel tries anyway, but is shocked to find that the cards say death. Lucy doesn't believe in the cards, but remembers Ricky last night pretending to kill her. Jerry, Ricky's agent, calls on the phone, saying he's lined up a dog act. Lucy comes in the middle of a conversation, and thinks Ricky is going to kill her, when he is talking about firing the show girl. Ricky leaves for the club, but Lucy is terrified of him. She calls in Ethel and tells her that her fortune is true. They find a gun in Ricky's desk, and think it's the murder weapon.
Later, Ethel comes back to the Ricardo's apartment to find Lucy hiding in the kitchen, wearing a pot and trash can lid in front and behind her as bulletproof bests. Ricky comes home, and Ethel flees. Lucy continues to dodge Ricky, and Ricky tries to calm her down. Lucy hides in the closet and locks the door, and Fred comes in to help. Fred suggests to slip her a mild sedative to calm her down. Lucy comes out of the bedroom and sees Ricky slip the sedative into the drink, thinking it's poison. Lucy tries to switch them while distracting him with dancing, but Ricky switches them again. Lucy is shocked, and thinks she's been poisoned and is about to die, although she just falls asleep. Ethel comes in after Ricky leaves, thinking she's dead until Lucy wakes up. They decide to go down to the club and plans on kill Ricky before Lucy dies.
At the club, Lucy comes down pointing the gun at Ricky. Ricky explains that the dogs are the names of the girls, and that the gun is a prop in the Western numbers. Lucy forgives him, and they forgive each other. That evening, Lucy is immersed in the book again, and throws it out of the window again when Ricky scares her. This time, she tied a string to the book and reels it back in.