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 Colt so that it can again kill "anything,"
and also shows them a knife in her possession that can kill anything.
Later, they learn from her that all demons used to be human, but had their
humanity burned away slowly in the fires of Hell. Dean begins to train
Sam to fight demons alone once he is gone.
During the course of the season, the brothers meet up with another beautiful
woman, Bela Talbot, numerous times. Bela acquires magical objects and
sells them for a large profit, and is unscrupulous and seemingly amoral.
In "Dream a Little Dream of Me", Bobby falls into a coma, and
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 future, demonic version of himself in a nightmare, which shocks him
into starting to fight for his life and to realize he is not worthless.
After waking up, Dean admits to Sam that he doesn't want to die. Meanwhile,
Bela steals the Colt, meaning they won't have it to fight with when the
Hellhounds come for Dean.
In "Mystery Spot", Sam is forced to relive the same day, a
Tuesday, repeatedly. On each new day, Dean dies a different way despite
Sam's frantic efforts to save him. Sam realizes that the culprit is the
Trickster, a villain from Season 2. It finally becomes Wednesday, but
this time, Dean dies and doesn't come back. Sam spends months trying to
hunt down the Trickster, who reveals that he's 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 then
sends Sam back to Wednesday, despite Sam failing to learn the Trickster's
lesson.
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 they have lost the Colt. She says that she knows of a spell that
will destroy all the demons nearby, including herself, and that she is
willing to die in order to help Sam. However, they will need the heart
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, and Ruby was
ready to follow Sam. Now, Lilith has stepped into the power vacuum.
Dean continues to search for a means to save himself from his fate, but
ultimately is told by Ruby that there is no way to get him out of his
deal. 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 has been taken to Hell. As the brothers search
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 and her demon forces in a last-ditch
effort to protect Sam and save Dean's soul, Ruby appears and the three
are chased into a room by a hellhound that has come for Dean. Dean quickly
recognizes that Ruby's human host is now possessed by Lilith, not Ruby,
but it's too late. She sics the hellhound on Dean, killing him, before
trying 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 by seemingly endless chains and hooks through his flesh, crying out
in agony for Sam's help.
Source: wikipedia.org
