On a dark night when Steve is away, Robbie and his date are frightened by a man in a trench coat. It all happens when Robbie is seen putting on the hubcap of his next door neighbour. Steve isn't too concerned when he hears about the incident as he thinks it all stems from Robbie's steady diet of spy and mystery stories.

Chip begins to think it would be great to be an older brother, so he wishes for a little sister. After the new Hawkins family move into the vacant house across the street, a wild sequence of events results from an improbable case of mistaken identity -- an infant is somehow confused with a leg of lamb left in the boot of Steve's station wagon.