In West Dallas, Texas, finding himself in considerable debt, with loan sharks threatening to kill him, 22-year-old drug dealer Chris Smith (Emile Hirsch) decides the only solution is to murder his birth mother, Adele (his dad's ex-wife) to collect the $50,000 of insurance money. He has been told by his mother's boyfriend Rex that the sole beneficiary will be Chris' younger sister Dottie.Assuming Dottie would share any money, she gets with them, Chris tries to rope his father, Ansel, into a conspiracy to kill Adele - who is Ansel's ex-wife - to get the money. Chris tells his dad that he has heard of a guy who can help them - Joe Cooper (Matthew McConaughey), a police detective who has a side career as a contract killer. Ansel eventually agrees, planning to split the money four ways between themselves, Dottie, and Ansel's new wife Sharla. Dottie hears the plan as they are talking and agrees that it's a good idea.The plan almost fails when Chris is unable to front Joe's fee. However, Joe met the odd, childlike Dottie when he came to their mobile home to discuss the details and offers to take her as a "retainer" until the insurance comes through. Through Dottie's interaction with Joe, it is revealed that Adele (her mother) tried to kill her once when she was an infant. Joe "dates" Dottie and then appears to be staying over at their home and having sex with her regularly. Chris has a change of heart and asks him to call it off, unaware that the killing has already happened. But he finds out quickly enough when Joe calmly enlists his help to move the body and torch the car they put it in.After Adele's death is discovered, the family learns that the insurance claim actually pays to Adele's boyfriend Rex, not to Dottie. Ansel and Sharla confront Chris about this, and he admits he originally heard the details about the policy from Rex, who also originally told him about Joe. The family all realize that Chris has been duped into hiring someone to commit this murder. Immediately afterwards, Chris tries to talk his sister into running away with him to escape the loan sharks. Dottie says she will go with him, but she must see Joe again first.Ansel and Sharla go back to their home after the funeral. Joe is already there with Dottie. He comes out of her room and begins asking seemingly casual questions of Sharla. They become more and more pointed until ultimately, they force her to admit that she knew the policy was really $100,000 (accidental death is double). Joe also has retrieved some nude photos of Rex which Sharla had taken which Joe uses to prove to Ansel that she has been having an affair with Rex. Joe also shows them a check he has obviously taken from Rex, payable to Rex for $100,000. Angered, Ansel declines to protect Sharla when Joe punches her and forces her to simulate oral sex on a piece of fried chicken.Joe knows Chris is coming to take Dottie away and he threatens to murder Ansel and Sharla if they don't help him prevent Chris from taking her. Joe tells Sharla to put dinner on the table. After Chris arrives and they are all seated, Joe announces that he and Dottie will be married.Chris refuses to let them, ordering Dottie to leave with him, as Joe tells her to stay where she is. For a moment she sits there; then she gets up and turns and while the men yell out at her, Chris threatens Joe with a gun, and the two struggle. Ansel and Sharla jump in to assist Joe in pummeling Chris. In all the confusion, Dottie recovers the gun and in a rage, she fires several shots, killing Chris and seriously wounding Ansel. Dottie turns the gun on Joe, telling him that she is pregnant. Joe appears overjoyed as he inches closer to Dottie.The film ends just as Dottie moves her finger back on the trigger.