After the Springfield Retirement Castle is closed down because of too many violations, Homer has to take Grampa home. Marge decides to bring two of Grampa's friends home too when she learns that they don't have families to live with. Although he's initially annoyed by the old people, Homer realizes that he likes the old man lifestyle and begins acting like a septuagenarian.
Meanwhile, Bart sticks up for Nelson and wins the bully's friendship. He's made an honorary bully and is invited to attend a Bully Summit at Six Flags Over Krustyland. Someone takes a shot at the head bully and frames Bart for the crime. The Springfield bullies make their way home safely and are saved by a newly revived Homer.