After unfair treatment by his older siblings Linus and Lucy and getting in trouble at school, Rerun thinks that having a pet dog will cheer him up. He writes a letter to Santa Claus asking for a dog, but is later discouraged by the expensive costs of owning a pet and his mother's objections. Watching Snoopy dance to Schroeder's music, Rerun asks Charlie Brown if Snoopy has any siblings, and Charlie Brown shows him pictures of Snoopy's brothers and sisters. Rerun asks Charlie Brown if he can play with Snoopy sometime. Having fun with Snoopy, Rerun asks if he can take in Snoopy's brother Spike, an abandoned dog that has taken refuge in the desert.