The Keatons return home from a retro-showing of the Beatles' A Hard Day's Night. The parents loved reliving old times through the movie, but the children weren't so impressed. Alex complained that the songs kept waking him up; and Jennifer complained that without the breaking of guitars, she had no way of knowing when the song was over. Mallory wasn't thrilled with the movie, but it beat the movie Jennifer had picked last – one with subtitles.
But disagreement over the movie would prove to be the least of their worries that night. For Elyse goes into the living room, and discovers that the Keaton house was robbed that night. The burglars had taken – among other things – the breakfront containing thee Keaton silver, Alex's calculator collection and golf clubs, and Mallory's diary. Elyse calls the police.
The robbery changes the complexion of the Keaton household: they become suspicious every time they enter the house; the kids pay each other to look behind shower curtains; and Elyse was found frisking the paper boy, presumably for weapons. As the fear of living there builds, Steven calls a family meeting. Keaton family meetings are highly organized events: assigned seats around the kitchen table, minutes are read, and old business is discussed. Jennifer acts as family secretary, and Steven as president, presiding with a ladle for a gavel.
The business at hand is dealing with the robbery. A few guidelines are dictated: doors locked, call the police if they observe anything suspicious, and report where they are at all times. Alex and Jennifer are granted permission to sleep with nightlights. Mallory reports a feeling that she is being watched in her room, but Alex surmises that this is Marty Obeck from across the street.
The decision from the family meeting was to call a neighborhood meeting, and invite a police officer to speak. Experience with Jennifer's friend Crissy persuades Steven to host the meeting himself. Officer Becker from the police department paints a very gloomy picture of what the neighborhood might expect. When he loses control of the meeting, Earl Quigley, a neighbor who works in insurance, takes over. His outlook is gloomier than Becker's, and Earl recommends protecting themselves with a gun.
The prospect of gun ownership is repugnant to Steven and Elyse; Elyse vents that to friend and neighbor Phyllis Evans for support. But she learns that Phyllis already has a gun. Reluctantly, Steven and Elyse consider the possibility.
They go exploratory shopping, and Edna at the gun counter sees right through them – she's seen it before. Once robbed, pacifists turn to a gun. Edna recommends a model popular with pacifists, and they bring the gun home. For safety, they decide to keep the gun and the bullets in separate drawers.
They call in the kids to show them. Jennifer asks to take it to school for show-and-tell; Mallory prefers that there be no gun; and Alex muses that the gun could have been bigger.
That night, Alex had scheduled a sleep-over with Jimmy Barkham. But a fight over Social Security – Jimmy was for it – brings him home early. As Alex enters the house, Steven and Elyse perceive an intruder. Steven grabs his tennis racket, and traps Alex in the closet. The misunderstanding is explained, and the matter is cleared up.
When Steven discovers that he grabbed the tennis racket, not the gun, they conclude that it is pointless to own the gun. They make plans to return it in the morning.