Killers of the Flower Moon” is over three hours long. set in the 1920s and is about bad people doing bad things, all in the name of, shocker here, oil. A series of deaths on tribal land in Oklahoma …Killers of the Flower Moon” is over three hours long. set in the 1920s and is about bad people doing bad things, all in the name of, shocker here, oil. A series of deaths on tribal land in Oklahoma …