The wife of popular Florida Congressman (and prospective Senatorial candidate) Clegg Caffery is murdered. FBI Special Agent Matt Thurston begins an investigation that leads him from the Pentagon to the small town of Clewiston, Florida, in search of a photographer responsible for the photo found in the murdered woman's hand. He arrives too late. The man has committed suicide. Although Thurston uncovers a strange and suspicious story about the dead photographer that he believes is worthy of continued investigation, he is abruptly steered away from the case by his superiors.

Angered by this turn of events, Thurston enlists the assistance of two reporters. With their involvement, he begins to peel away layers of lies and deceit hiding the truth about the murder. Along the way, Thurston slowly unravels a complex weave of story lines that includes a sex for hire plot involving the President's wife; an attempt by computer magnate Norman Bremen to subvert the workings of Congress to ensure the survival of his sugar interests in Florida; and the revelation of a cover-up of a war crime in Vietnam that threatens the Presidency.

Although Evil Town is a work of fiction, it is based on historical and current events. The Vietnam element of the plot delves into the massacre of Vietnamese villagers at Co Luy. This occurred on the same day as the My Lai killings and happened as described in the novel. The military and political cover-up of the incident detailed in Evil Town is an interpretation of actual events that relegated Co Luy to the back pages of history.

The description of the political maneuvering related to the restoration of the Everglades, and to the "sugar wars" in Florida, is a dramatization of the intrigue currently being played out by power brokers, the media, and Congress on this issue.