Society has always had an ingrained fear of strangers. In more primitive or rural societies, where attitudes might be governed by legends and/or superstition, people who were ill might be regarded as possessed. False claims and public hysteria could lead to people being executed as in the Salem witch trials.
The present story is set in the rural bayous of Louisiana during the early 1940s. This is Cajun country, with attitudes passed down from the Acadians with origins in France. The wealthiest man in the parish has been brutally killed and a young woman was found near the body. She appears ill and delirious. Rumors arise that she is a werewolf. While being treated by a local herbal specialist, Madam Louiselle, she disappears into the night.
Deputy Sheriff Raymond Thibodeaux is investigating, but must deal with a variety of problems. This was a time when prisoners from the state prison at Angola were leased out to plantation owners to be used as what amounted to slave labor (the ancient practice of selling criminals into slavery). The unsavory victim of the crime, a man not well liked, had been using such laborers, one of whom is believed to have escaped. There are a large number of people who had reasons for wanting the man dead.
Various characters come into play. There is a Catholic priest assigned to the parish (he would have preferred to be in Ireland). There is a local doctor dealing with various illnesses and injuries. There is the Sheriff, who seems more concerned with politicing than police work. There is the sadistic boss of the work crew on the plantation. There is the brother of the missing woman, who lives in the marshes with his dogs. There is the postmistress, a woman who has managed to break into a government job normally reserved for men. And there is a local prostitute who would really rather be a teacher if events in the past had not taken a bad turn.
Raymond, who was discharged from the Army with a disability, must deal with the ghosts from his own past as he tries to head off mob hysteria, find the missing woman, and try to solve the case. It is a dark tale worth reading.