Doreen McKay

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.

Foreign agents are smuggling monium (a chemical used in producing poison gas) into Mexico. The three Mesquiteers get involved when they ride to save a girl (really a government agent) on a runaway horse.