Early reviews praised Carnivàle for style and originality but questioned the approach and execution of the story. The first episode set an audience record for an HBO original series and drew durable ratings through the first season.  When the series proved unable to sustain these ratings in its second season, the series was cancelled. An intended six-season run was thus cut short by four seasons.
In all, 24 episodes of Carnivàle were broadcast. In 2004 the series won five Emmys out of fifteen nominations. The show received numerous other nominations and awards between 2004 and 2006.
The two seasons of Carnivàle take place in the Depression-era Dust Bowl between 1934 and 1935, and consist of two main plotlines that slowly converge. The first involves a young man with strange healing powers named Ben Hawkins (Nick Stahl), who joins a traveling carnival when it passes near his home in Milfay, Oklahoma. Soon thereafter, Ben begins having surrealistic dreams and visions, which set him on the trail of a man named Henry Scudder, a drifter who crossed paths with the carnival many years before, and who apparently possessed unusual abilities similar to Ben's own.
The second plotline revolves around a Father Coughlin-esque Methodist preacher, Brother Justin Crowe (Clancy Brown), who lives with his sister Iris (Amy Madigan) in California. He shares Ben's prophetic dreams and slowly discovers the extent of his own unearthly powers, which include bending human beings to his will and making their sins and greatest evils manifest as terrifying visions. Certain that he is doing God's work, Brother Justin fully devotes himself to his religious duties, not realizing that his ultimate nemesis Ben Hawkins and the carnival are inexorably drawing closer.