1890. Clare Wright, a talented young detective with a surprising past, has just resolved her latest case for the Pinkerton agency when her career takes an unexpected turn for the American frontier. Fred Harvey, founder of the famous Harvey House hotels, wants to know who is perpetrating the robberies affecting his new enterprise in Montaña Roja, New Mexico, and he needs an undercover agent who can discover the truth.

Disguised as one of Fred’s renowned hostesses, the Harvey Girls, Clare must infiltrate both low and high society as she seeks out the culprits. But with the town a hotbed of crime, and with schemes underway that could have implications for the whole nation, she’ll need to make sure her derringer is never far away.