Ten-year old Ted Dodd is on a driving trip with his parents and his beloved German shepherd dog Buddy, when a reckless driver swerves into the path of his parents' car, sending the vehicle plunging into a ravine, where it bursts into flames. Ted's parents perish in the conflagration, but Buddy pulls his young master to safety. Speeding to the accident scene, a rescue squad finds Ted and takes him to the hospital in an ambulance, but not realizing that Buddy is Ted's dog, they leave the canine behind. With only the sound of the ambulance's siren as a clue to Ted's whereabouts, Buddy returns to the wreck, where he finds his master's baseball glove, which he picks up with his teeth. Knowing only that Ted was taken away in a vehicle with a siren, Buddy races after police cars, fire engines and ambulances in a desperate search for his missing master. At the hospital, meanwhile, Ted is in shock and unresponsive to the care of his physicians, Dr. White and Dr. Lusk. The police, on the alert for missing show dog "Sir Rex," owned by millionaire breeder Jim Foster, find Buddy, and thinking that he is the missing dog, take him to Foster's estate. Although Foster realizes that Buddy is not his missing dog, he is determined to win the championship in the upcoming dog show and enters Buddy as Sir Rex. Meanwhile, when Ted responds to a drawing of a dog, his doctors decide to take him to the dog show, hoping to rouse him from his state of shock. At the show, after Buddy is awarded a blue ribbon, he hears a fire engine outside and bolts from his leash to pursue it. Spotting Buddy, Ted watches helplessly as the dog runs into the city streets. Noting Ted's response to the dog, the doctors tell Foster that they think Buddy belongs to Ted. Foster then admits his ruse, and after returning the ribbon to the judges, drives off in his limousine with his wife Jane, Ted and his nurse to search for the dog. While stopping to rest at a shady ravine, they hear a siren, a signal from a nearby rock quarry to clear the area for blasting. Hoping that Buddy will follow the sound of the siren, Ted dashes into the quarry, and from the quarry floor, sees Buddy standing on a cliff. When Ted calls to his dog, Buddy threads his way through the flying debris and exploding dynamite to find his master. The Fosters and the nurse reach Ted and Buddy in the quarry take and them to the Foster home, where the Fosters welcome Ted and Buddy into their family.