The H in HBO doesn’t stand for happy.

Series such as “Oz,” “The Wire” and “Six Feet Under” don’t exactly put a smile on people’s faces. That tradition continues with the cabler’s next original grim series, “Carnivale,” which will bow Sept 14.

Set against the Great Depression, with evil on the rise around the globe, the skein follows a carnival as it travels across the Oklahoma Dust Bowl. Clancy Brown (“ER,” “The Shawshank Redemption”) plays a small-town preacher and Nick Stahl, who starred opposite Marisa Tomei in “In the Bedroom” and appears in “T3” this summer, is a mysterious fugitive taken in by the carnival.

“‘Carnivale’ is a dark, intriguing drama that works on many levels,” says HBO chairman-CEO Chris Albrecht. “The series continues HBO’s tradition of presenting shows that can’t be found anywhere else on TV.”

Also starring are Adrienne Barbeau, Amy Madigan, Clea DuVall, Michael J. Anderson and Kim DeKay. Two members of the Cirque du Soleil troupe have recurring roles.

“Carnivale,” which has a 13-episode commitment, has a list of directors that includes “The Sopranos” helmer John Patterson, Rodrigo Garcia and Scott Winant.

Ronald D. Moore, Daniel Knauf and Howard Klein are exec producers.