Spoiler warning: this article reveals major events and the ending of Supernatural Season 4.
Season 4 of Supernatural builds its central conflict around 66 seals that keep Lucifer imprisoned. Dean Winchester is brought back from Hell by Castiel, only to discover that what happened to him there broke the first seal. Meanwhile, Sam grows closer to Ruby in an effort to defeat Lilith, unaware that killing her is exactly what will break the last one.
Originally aired from 2008 to 2009, the season has 22 episodes. This recap traces the Apocalypse storyline and the decisions connecting its key turning points, rather than offering a separate synopsis of every episode.
Dean returns from Hell, and Castiel reveals a larger war
In Lazarus Rising (4x01), Dean reappears after dying at the end of the previous season. The question of who brought him back is answered by Castiel, who identifies himself as an angel. The show's supernatural world expands beyond demons and individual hunts into a struggle involving Heaven and Hell.
In the next episode, Are You There, God? It's Me, Dean Winchester (4x02), the appearance of spirits called the Witnesses is linked to the seals. Castiel explains that Lilith is trying to break the barriers keeping Lucifer locked away. The danger does not hinge on a single ritual in the finale: every event used as a seal brings the prison closer to opening.
What are the 66 seals, and why is Dean tied to the first?
The seals work like symbolic locks. They are specific events, not 66 physical objects for Sam and Dean to find. The season's explanation mentions roughly 600 possible seals, of which 66 must be broken. That is why stopping one particular threat is not enough to defeat Lilith.
The most painful discovery comes in On the Head of a Pin (4x16). During his confrontation with Alastair, Dean learns that the first seal broke when he gave in to torture in Hell and began torturing other souls. Its condition was that a righteous man shed blood there. Castiel confirms Alastair's revelation.
Dean therefore returns not simply to fight a distant catastrophe, but to discover that he has already been used to set it in motion. That knowledge explains his guilt and makes Castiel's claim that the righteous man who began the process has a crucial role in ending it much harder to bear.
How Ruby leads Sam toward Lilith
Sam believes his powers against demons may offer an answer to the advancing seals. Ruby encourages that belief and urges him to drink demon blood to strengthen his abilities. The increased power is real within the story, but it comes at a cost: Sam becomes dependent on it and starts hiding his choices from his brother.
Dean sees Ruby's influence as dangerous; Sam interprets Dean's resistance as an unwillingness to accept what he believes is the only way to stop Lilith. In When the Levee Breaks (4x21), Dean and Bobby lock Sam away so he can go through withdrawal. Acting on orders Sam knows nothing about, Castiel lets him escape. Later, Sam protects Ruby from Dean, and their confrontation ends in a serious rift.
Ruby's manipulation works because it is built around a legitimate goal: preventing the Apocalypse. The deception lies in what she withholds about the consequences of Lilith's death.
The truth about the angels changes the mission
The appearance of angels does not mean they all want the same thing. The conflict involving Uriel, exposed in 4x16, already reveals divisions among them. In the finale, Lucifer Rising (4x22), Zachariah discloses something worse: the leaders of Heaven he represents want the Apocalypse to happen because they expect to defeat Lucifer in the war that follows, despite the human cost.
Dean realizes that his supposed mission to prevent the prison from opening has been managed by celestial authorities who actually want that outcome. Castiel, meanwhile, chooses to disobey those orders and helps Dean try to stop Sam. His choice matters because it separates an angel's individual conscience from the agenda of his superiors.
Why does Lilith's death free Lucifer?
Ruby promotes the idea that Lilith could break the final seal. The decisive revelation turns that logic on its head: Lilith's sacrifice is the final seal. Killing her does not prevent Lucifer's release; it completes the sequence that opens his prison.
Castiel reveals the truth to Dean when Sam is already about to act. At the convent where the final confrontation takes place, Sam uses his powers to kill Lilith despite hearing Dean trying to reach him. Ruby then celebrates and admits she guided Sam toward this outcome. Her alliance with him was part of the plan, not a genuine attempt to stop the Apocalypse.
Dean arrives and kills Ruby, but Lilith's death cannot be undone. Her blood marks the opening of Lucifer's prison, and the episode closes with his release underway. It is a cliffhanger, not a definitive battle between the brothers and Lucifer.
Timeline of the main story arc
- 4x01: Dean returns from Hell, and Castiel enters the story.
- 4x02: Lilith's plan involving 66 seals becomes clear.
- 4x16: Dean learns he broke the first seal while in Hell.
- 4x21: Sam's dependence, Ruby's influence, and his conflict with Dean reach a breaking point.
- 4x22: Zachariah reveals Heaven's leadership wants the Apocalypse; Castiel defies his orders.
- 4x22: Sam kills Lilith, the final seal breaks, and Lucifer is released.
What Season 4 resolves
Season 4 reveals who broke the first and last seals, how Sam and Dean were steered by allies with hidden agendas, and why Castiel's intervention comes too late. The 66 seals provide the mechanism of the Apocalypse, but the emotional core is a clash between brothers who both believe they are saving the world through incompatible methods. Lucifer's release ends that chain of events while leaving its consequences for the next chapter.
