Det. Scott Turner (Tom Hanks) is an uptight, by-the-book police officer who hopes to leave his sleepy California town and work in the big city. When his friend Amos Reed (John McIntire), the proprietor of a junkyard, is killed, Turner reluctantly inherits the man's dog. Realizing that the canine may be able to help him solve the murder case, Turner attempts to adjust to life with the big dog, resulting in much household destruction and unwelcome chaos.