Sundown in Santa Fe is a thriller following a government agent trying to track down the man behind the assassination of President Abraham Lincoln. Rocky Lane (Allan Lane) is sent to Texas, seeking out Walter Durant. All of the leads point to Santa Fe, and Lane travels there, carrying the only clue left behind by Durant: a dagger with the words Sic Semper Tyrannis inscribed upon its blade. When Lane arrives in Santa Fe, he meets up with Tracy Gillette (Roy Barcroft), a rancher, and his beautiful daughter Lola Gillette (Jean Dean), and races to uncover the whereabouts of Durant and his devious gang. However, Lola may be working with the gang, or they may be using her; this is a mystery that Lane must figure out, on top of finding out their actual location. In this Western, a sense of mystery and suspense separates Sundown in Santa Fe from other movies in the genre.