Lisa has the mumps and has to spend a few days home from school. While Marge teaches Lisa sewing, Homer goes to the mall to buy some magazines for her. There he sees and purchases some $125 shoes known as the Assassins, which he saw his neighbor Ned Flanders wear earlier. However, Santa's Little Helper promptly destroys the shoes, angering Homer. Marge shows Lisa a patchwork quilt, which is a family heirloom. Lisa makes her own contribution to it, but then Santa's Little Helper rips it up. When Homer discovers that Santa's Little Helper has also eaten his cookie, which Homer had bought earlier, he demands that the family get rid of the dog and laughs at the kids when Marge agrees with him, but the kids, terrified that Homer will take away their pet, promise their dad that they will train their dog to prevent future circumstances.
Santa's Little Helper does not do well at the obedience school as Bart is reluctant to use a choke chain suggested by the school's instructor Emily Winthrop. The night before the final exam, Bart and Santa's Little Helper play, thinking it will be their last few hours together. This bonding breaks down the communication barrier, meaning Santa's Little Helper can understand Bart's commands, and much to Homer's chagrin, passes obedience school. Lisa marks the occasions by starting a new quilt to replace the one destroyed.