Swan Song

Summary
All out of options, Dean Winchester reluctantly agrees on letting Sam be the host for Lucifer so that he can jump into Lucifer's Cage. Remembering what Lucifer said to Dean in the future, they locate him in Detroit. Sam makes Dean promise that if things go as planned, he will make a life for himself with Lisa Braeden. After consuming gallons of demon blood, Sam and Dean allow themselves to be caught be demons and brought to Lucifer. After demonstrating his enhanced powers to kill the demons in the room, Sam consents for Lucifer to possess his body.

It is then that Lucifer reveals that he knows that the Horseman's rings form the keys to his cage, and that he is wary of the boys' plans to trick him inside. Nevertheless, he agrees to possess Sam and let him try to retain control of his body. After Lucifer enters Sam, he is knocked unconscious, and Dean quickly throws the key to the cage on the wall and opens it with a spell. After waking up Sam, he watches him preparing to enter the pit, but instead Lucifer then reveals that he overpowered Sam in a matter of seconds. He then closes the portal, puts the key into pocket and quickly disappears.

Outside, Dean meets back with Bobby and Castiel, and they observe various natural disasters on television that are occurring around the world. Knowing that Lucifer will try to seek out Michael for their final battle, they call Chuck to get the exact setting for the fight: Noon at Stull Cemetery in Lawrence, Kansas. Elsewhere, Lucifer is reveling in his new vessel while addressing Sam, who is still fighting him from the inside. He tells Sam that he only wants the best for him, and even offers to spare Dean after the world is destroyed. In a show of goodwill, he brings several people from Sam's past - including a former teacher of his and a prom date - and tells Sam that they were all possessed by demons working for Azazel in order to manipulate him. He then offers Sam revenge on them, and then asks him afterwards if he enjoyed it.

Lucifer is seen standing in the cemetery when Michael, who now possesses Adam, arrives. While Lucifer tries to dissuade him from fighting, Michael regretfully tells him that he must do so because God wishes it. Before the get underway, Dean, Castiel and Bobby arrive on scene and Castiel throws a Molotov cocktail of Holy Oil on Michael, forcing him to temporarily vanish. Lucifer, outraged at Castiel's action, blows him up with a snap of his fingers, then snaps Bobby's neck after he is shot with the Colt. Dean repeatedly appeals to Sam to overpower Lucifer, who responds by severely beating him until he is barely conscious. However, as he presses Dean against the side of the Impala, ready to deliver another blow, he pauses as he catches sight of a plastic army man in the ashtray of one doors.

This triggers memories of Sam's childhood and various warm moments with Dean, which allow Sam to finally overpower Lucifer. He then opens the cage with the Horsemen's rings, when Michael suddenly returns. He says that he won't let it end the way Sam wants it to and charges at him. Sam, now in control, pulls Michael with him into the cage and the portal closes. Castiel then reappears and tells Dean he was resurrected by God and promoted. He then heals Dean and resurrects Bobby.

As they drive home, Castiel mentions that with Michael gone, he intends to take charge of Heaven and disappears. Dean leaves Bobby and heads for Lisa's house where she gladly welcomes him in. Meanwhile, Chuck, who has been narrating the entire story while writing on his computer, smiles as he brings an end to the story, only to state that "nothing ever really ends, does it?". He then vanishes into thin air with a smile, wearing a white shirt instead of his usual drab clothes.

Outside of Lisa's house, a streetlight outside goes out and Sam is shown standing beneath it, watching Dean through the window.

Major Characters

 * Dean Winchester
 * Sam Winchester
 * Castiel
 * Bobby Singer
 * Lucifer

Minor Characters

 * Chuck Shurley/God
 * Michael (Adam Milligan is his host)
 * Lisa Braeden
 * Benjamin Braeden

Trivia

 * Chuck is the alter ego of God.
 * This episode marks the final appearance of Lucifer, Michael, and Chuck Shurley
 * Bobby dies for the first time on-scene.
 * Lucifer mentions Hell is cold.
 * The title is probably called Swan Song probably because it dual reference to Sam Winchester's last great act before his death and to the last episode produced by the showrunner; Eric Kripke, before he stepped back to allow others to head up the sixth season.