The agents set up a sting operation to catch a gang which has been robbing stagecoaches, but Averi Trent, the territorial governor's daughter, gets in the way and is kidnapped. West goes after the gang while Gordon, at the relay station where the stagecoach was originally headed, learns that the outlaws are carrying a highly communicable, deadly disease. West does his best to get an unhelpful Trent away from the outlaws while Gordon tries to locate West, the girl and the gang before it's too late for the medicine he's carrying to save them.
Tropes present in this episode:
- Identical Stranger: In the tag scene, the Girl of the Week introduces our heroes to her fiancÚ, who is played by Robert Conrad with a moustache.
- The Plague: The plague which the title refers to is "Noguri's Syndrome," which, as Artie learns, is a highly communicable and generally fatal disease originating in Asia. It can be cured if an inoculation is received within three to five days after infection.
- Stock Footage: Like the previous episode, this borrows footage from a season three episode (in this case, the shots of Jim lowering himself down a cliff face as part of his attempt to rescue Averi (which doesn't work) come from "The Night of Jack O'Diamonds").