It’s 1851, and brothers Charlie and Eli Sisters have been dispatched to kill Hermann Kermit Warm at the behest of their boss, a man who goes by the name The Commodore. (Warm’s crime: Stealing from the Commodore, obviously.)

The brothers set off for San Francisco, the last known address of Warm, but of course nothing goes as planned: There’s an incident with a bear and some panning for gold, among other hijinks.

Brother Charlie is a sociopath, a fan of whiskey and women, whereas Eli is calmer and far more interested in moving past the whole “contract-killing” business.

Equal parts comic sendup of the Old West and a depiction of its brutality, the 2011 book “The Sisters Brothers” by Patrick deWitt (author of the new title “French Exit”) will have its film release on Sept. 21. The film stars Jake Gyllenhaal, Joaquin Phoenix and John C. Reilly.