A young man and his trusty dog go up against a gang of crooks that are building a dam out of shoddy materials, which could collapse and flood the entire valley.
Daredevil flyer David flirts with a waitress. An orphan accidentally takes off in a biplane requiring an aerial rescue. The villain reports a fake robbery and turns the orphan in to welfare workers, but a loyal dog saves the day.
Two men are rivals for the same girl. When she finally agrees to marry one, the other--appearing to be magnanimous in defeat--presents his former rival with a beautiful German Shepherd dog as a wedding present. It turns out, however, that he had an ulterior motive--he had trained the pooch to allow absolutely no one to get near the young woman. Complications ensue.
The Three Mesquiteers are forced to track down a train robbery ring after some of the gang hijack their truck for a getaway and the police conclude they are part of the gang, an identification which is just fine with the gang's nameless chief.