Rin Tin Tin witnesses a murder for which his master is blamed. Rinty knows who committed the crime, and sets out to track down the killer and clear his master's name.

Paul Andrews sets out to find his missing sweetheart with the aid of Buddy, his dog, after returning from wartime service. They hop a freight to a lumber camp, and upon rescuing a girl from Martin Dains they discover her to be his sweetheart, Caroline. When Martin kills the girl's stepfather suspicion falls on Paul, but a confession is wrested from the villain by Buddy.—Pamela Short