Coop, a 10-year-old boy is constantly fighting his sister’s cat, who is actually an alien. Once his younger sister brings home a stray cat named Mr. Kat, and Coop’s life turns upside down. Kat believes that it is Coop’s fault that he was thrown to Earth, so he constantly hatches plans to turn his life into agony. The boy is forced to confront the cat alone, as there is no evidences of cat’s alien origin, and no one believes Coop’s stories about the evil cat.