It focuses on a gang of outlaws who find their way to a hidden valley and a peaceful town, where residents shun swearing, alcohol, guns, and any kind of violence, but resemble dead Western heroes.

The gang flees, pursued by a posse, and manages to escape through a dust storm by following a tunnel into a green valley.

These include Wild Bill Hickok, the town's sheriff; Jesse James; Billy the Kid; and Doc Holliday, although they deny their identities to Sonny.

While talking to Doc, Sonny lets slip the true nature of their gang and the sheriff asks them to saddle up and leave town.

The townspeople are summoned by the church bells, but while most of them comply, Hickok, Holliday, James, and Billy all join Sonny, inspired by his willingness to die to protect Rose.

Hickok and the others grimly follow, but the stagecoach arrives and the driver tells them that by their willingness to sacrifice their chance of a better future to protect the others, they have secured a place in Heaven.

Writer Gordon Dawson had worked on several Westerns previously, and was inspired to write a religious morality tale set in an Old West town inhabited by ghosts.

[4] Director Uli Edel had always wanted to direct a Western, but was aware of the genre's dwindling popularity with the major Hollywood film studios in the late 1990s, as were Purgatory's producers.

[9] Anita Gates of The New York Times' was also enthusiastic about this “fascinating, deceptively dark Western with more than a touch of The Twilight Zone,'' observing, "Gordon Dawson's script makes the process satisfying despite the fact that any viewer who has noticed the title of the film knows the answer from the beginning.

[11] Hugh H. Davis later provided a chapter examining Purgatory's surreal and religious themes in the compilation Undead in the West.