Young widow Louise Pearlie seizes a chance to escape the typewriters and files of the Office of Strategic Services, the United States' World War II spy agency, when she's asked to investigate a puzzling postcard referred to the OSS by the US Censor. She heads off to St. Leonard, Maryland, to talk to the postcard's recipient, one Leroy Martin. But what seemed like a straightforward mission to Louise soon becomes complicated.

Leroy and his wife, Anne, refuse to talk, but as Louise investigates, it soon becomes clear that Leroy is mixed up in something that looks a lot like treason. But what? Louise is determined to find out the truth, whatever the cost ...