Mandy and her son Aiden live with her boyfriend, Cal Garrigon. They take in a dog, Lucky, who grows attached to Mandy and kills anyone who threatens her and her son: their landlord because they are behind on the rent, Cal's brother because he was violent towards Mandy, and eventually Cal, who is a drunk.
After being hit by a car while in dog form as he fled Sam, Sam and Dean take Lucky from the animal hospital, binding him in rope and silver chains to restrain him. He reveals that there are about thirty skinwalkers who have been recruited and are living with families as pets. One signal from their pack leader, and they will infect their families, thus recruiting more skinwalkers. He tells Sam and Dean that there are packs in many other towns, but he knows nothing of the Alpha Skinwalker. Mandy and Aidan were Lucky's targets for transformation, but he grew to genuinely care for them and agrees to help take down his pack to protect the two.
Lucky leads Sam and Dean to the Pack Leader, but he has kidnapped Mandy and her son and threatens to kill them unless Lucky turns them. As a confused and frightened Mandy watches the confrontation, the Winchesters attack and Lucky leads Mandy and Aidan to safety inside of an office. Lucky protects Mandy and her son from the Pack Leader's Second in Command, revealing that he is her dog in the process. Although Lucky is wounded protecting them, the second in command is killed in time by Dean Winchester and Lucky flees.
Lucky in human form, goes to visit Mandy and tells her how he appreciated her kindness, but she tells him to leave. Lucky transforms into a dog and dejectedly leaves.