John Wayne stars with Ann-Margret as a gunman who agrees to help a beautiful widow cross into Mexico to retrieve a fortune in gold stolen by her late husband. Mrs. Lowe (Ann-Margret) tells Lane (Wayne) that she just wants to clear her family name, and she offers the reward for the return of the loot as payment. Now, with a band of friends, Lane and Lowe go after the gold. But they are not the only ones looking for the stolen fortune ... and the lovely Mrs. Lowe has secrets of her own that may doom The Train Robbers.