No one in Simpson family notices when Santa's Little Helper becomes seriously ill. While the family watches TV for the winning lottery numbers, the dog collapses. They rush him to the hospital, where they learn that he needs a $750 operation. The Simpsons do not have the money, but when Santa's Little Helper licks Homer, they resolve to find a way to help him.

In order to afford the operation, everyone in the family has to sacrifice something. Homer gives up beer, and Marge cooks no-frill meals. The operation is successful and Santa's Little Helper is completely healed. The Simpsons, however, are forced to live a life of austerity and take their frustrations out on the dog. One night, Homer inadvertenty leaves the gate open and Santa's Little Helper wanders off. Guilt stricken, the family misses him and tries to find him.

Santa's Little Helper is picked up by the dog catcher and taken to the pound, where Mr. Burns sees him and adopts him as one of his attack dogs. When Bart enters Burns's mansion, looking for his dog, Burns releases the hounds. Santa's Little Helper remembers Bart and saves him from the other dogs. Bart takes Santa's Little Helper homer, where he receives a warm homecoming.