The Three Mesquiteers convince a group of settlers to exchange their present property for some which, unbeknownst to our goodguys, is going to be worthless. They are captured before they can warn the ranchers.
The Cattlemen's Association has called in the Mesquiteers to find cattle rustlers. They get Tex Riley to pose as Stony so Stony can arrive posing as a wanted outlaw. This gets Stony into the gang of rustlers and he alerts Tucson and Lullaby as to the next raid. But Hartley is on hand and unknown to anyone is the rustler's boss and he joins the posse with a plan that will do away with the Mesquiteers.
After gold shipments from a mining town have been hijacked, the three Mesquiteers buy a plane to fly the gold out. The owner of the shipping line brings in Eastern gangsters to thwart them.
Flagg is relocating flood victims to Gunsmoke Ranch. The Three Mesquiteers know Flagg to be a crook and try to warn them.
The Mesquiteers capture a horse thief who escapes justice through a crooked judge. They gather signatures urging the governor to investigate but a friend with the petition is murdered. Stony is accused.
Cattle are being routinely stolen from a local ranch, and suspicion centers on a local mountain family. But the Three Mesquiteers are wise to the criminals' deeds. But when a ranger is shot and Stony is framed for the crime, it's up to Lullaby and Tucson to prove his innocence.
Talbot uses a phony land grant to rule thirteen million acres, taxing everyone heavily and evicting those who won't pay. The Three Mesquiteers becomes mysterious "night riders" to fight this evil.
The first of eight "Three Mesquiteers" Westerns to star John Wayne.