U.S. Treasury agent Jack Wood is trying to find the source of counterfeit money appearing in Texas border towns when he suddenly disappears in El Paso. The U.S. deputy treasury director informs a select group of President Ulysses S. Grant's advisors of Wood's disappearance and of Mexico's possible involvement with the counterfeit money.
South of El Paso, Mexican mercenaries assemble with orders to destroy the town, seize Dallas, and hold Texas hostage until Grant exchanges the state for thousands of American lives. Grant hesitates. His administration, fraught with scandal, is not trustworthy. With the post-Civil War depression and military downsizing, America can ill-afford another war.
With instructions from Washington, a half-dozen Texas Rangers descend on El Paso, only to learn that Wood is being held captive in Mexico. With the Mexican government in revolt, crossing the Rio Grande would be considered an act of war.
Ellsworth T. Kincaid, Jack's friend and a dime-novel celebrity, and Stetson, his beautiful female companion, learn of Wood's whereabouts and resolve to rescue him. Crossing into Mexico, the couple penetrates the Mexican stronghold. But Stetson is apprehended, forcing Kincaid to make a stand against two hundred maniacal cutthroats.