Elizabeth Taylor stars as a girl who raises a Collie named Lassie from puppy to working ranch dog. But when Lassie is hit by a car and develops amnesia, she is sent to help fight the Japanese during World War II. She returns from the war a violent, dangerous dog, and the local townspeople decide she must be killed. Only the love of the girl who raised her can tame the violent behavior she learned in battle ... and spare Lassie's life.