Academy Award-winning Exorcist director William Friedkin scuttles deep into the darkest recesses of the traumatized human psyche with this tale of a lonely bartender haunted by the long-ago disappearance of her young son, and the paranoia that emerges when she enters into a tentative relationship with a deeply disturbed drifter. Adapted from the off-Broadway play by Tracy Letts, Bug centers on Agnes (Ashley Judd), who tends bar alongside pal R.C. (Lynn Collins), and has recently moved into a shoddy roadside motel in hopes of avoiding her menacing and recently paroled ex-husband, Jerry (Harry Connick Jr.). Upon making the acquaintance of subdued former soldier Peter (Michael Shannon, repeating his stage role), a veteran of the first Gulf War, Agnes finally senses that things are looking up. Quietly charming despite his melancholy aura, Peter soon reveals to Agnes that he contracted a "bug" while serving in the Middle East, and that it may have been deliberately administered as part of a secret military medical experiment. Convinced that the microscopic insects are quickly multiplying just under the surface of his skin and that they have now infected Agnes as well, Peter soon descends into a psychotic rage as he resorts to increasingly desperate measures to purge himself of the offending subdermal arthropods.