In the third season premiere "The Magnificent Seven," Dean decides to make the best of his final year, indulging in many pleasures and refusing to even think about saving himself, while Sam tries desperately to find a loophole in the Crossroads demon's deal. While searching for escaped demons to send back to Hell, Sam encounters Ruby, a mysterious blonde who assists him but who also informs him that, for some reason, demons are killing all of his mother's old acquaintances. Sam learns that Ruby is a demon, and she promises him help in freeing Dean from his contract. She fixes the コルト so that it can again kill anything and also shows them a ナイフ in her possession that can kill demons. Later, Dean and Sam learn from Ruby that all demons used to be human, but had their humanity is eventually burned away during their time in hell.
During the course of the season, the brothers meet another woman, Bela Talbot. Bela acquires magical objects and sells them for a large profit, and is unscrupulous. In "Dream a Little Dream of Me," when Bobby falls into a coma, Sam and Dean investigate the murder of a scientist. In the course of viewing Dean's dreams, it becomes clear that Dean believes that Sam was their father's favorite, but only thought of Dean as a tool. Dean encounters a demonic version of himself in a nightmare, which shocks him into trying to break his deal. After waking up, Dean admits to Sam that he doesn't want to die. Meanwhile, Bela steals the Colt.
In "Mystery Spot," Sam is forced to relive the same day, repeatedly. On each new day, Dean dies a different way despite Sam's efforts to save him. Sam realizes that the culprit is the Trickster, a villain from Season 2. They finally escape the day, but Dean dies and doesn't come back. Sam spends months trying to hunt down the Trickster, who reveals that he has been trying to get Sam to understand that he and Dean can't keep making sacrifices for each other, and that Dean is going to die no matter what Sam does. The Trickster allows Sam to escape the alternate reality he has trapped him in. He is warned によって Ruby that he might not make it back from hell.
In "Jus In Bello," the FBI and Agent Henricksen capture Sam and Dean, thanks to a tip from Bela. While Sam and Dean are in jail, a host of demons come to kill them. Ruby comes to help them, but is furious to learn that they have ロスト the Colt. She says that she knows of a spell that will destroy all the demons nearby, including herself. However, they will need the ハート, 心 of a virgin. Sam and the virgin, Nancy, agree to the plan, but Dean refuses to let her die. Dean's plan to exorcise the demons works, but one demon manages to escape and tells Lilith who, taking the form of a little girl, blows the police station up, killing everyone inside. Lilith, it turns out, wants to kill Sam, as she sees him as a rival. According to Azazel's plan, Sam was supposed to lead the demon army, but now Lilith is the leader of the demons.
Shortly before Dean's contract comes due, he learns from Bela that Lilith, the demon pursuing Sam, holds his contract; Bela had also made a deal with a demon, and she reveals this information before her contract expired. As the brothers 検索 for Lilith with Bobby's help, Dean begins suffering nightmares and hallucinations of his hellish fate. When Lilith is located, the three head to New Harmony, Indiana, and Dean discovers that he now has the ability to see the faces of demons underneath their human hosts.
As Dean and Sam confront Lilith, Ruby appears and the three are chased into a room によって a hellhound that has come for Dean. Dean quickly recognizes that Ruby's human host is now possessed によって Lilith, not Ruby, but it is too late. A hell hound kills Dean and Lilith tries to kill Sam, only to discover that her demonic power has no effect on Sam. Lilith flees, leaving Sam alone with Dean's mutilated corpse. In the last scene of the season, Dean is shown in Hell, suspended in a void によって seemingly chains and hooks through his flesh, crying out for help and for Sam.