After Courage sees a list of missing dogs, a flashback appears showing how Courage's parents got sent into outer space by an evil veterinarian. Muriel and Eustace take Courage to the same veterinarian to get him checked out. But the veterinarian plans to send Muriel and Eustace to outer space. Determined not to lose his owners like his parents, he must rescue them before they too suffer the same fate.
