Supernatural Season 6 premiered on September 24th, 2010 and concluded on May 20th, 2011. It consisted of 22 episodes beginning with the episode "Exile on Main Street" and ending with the episode "The Man Who Knew Too Much".
Season 6 begins with Dean living a "normal" life with Lisa and her son Ben. He is now working as a construction worker. Unfortunately, hunters never really leave their old life behind. His old life comes back to haunt him when a group of Djinn come after him, seeking revenge for their father's death. After Dean is poisoned, he is saved by Sam, who somehow is back from Hell. He is now working with Samuel Campbell, his grandfather, and his cousins. Both he and his grandfather are back to life but with no idea how it came about. It is later revealed the somehow, when Sam was resurrected, he was brought back without his soul. This leaves him with no feelings, emotion, or conscious. Dean makes a deal with the horseman Death to get Sam's soul from the pit and put back where it belongs, even though he is warned by Castiel that the soul has been locked in the cage with Michael and Lucifer for more than a year and is probably damaged beyond repair. Death puts up a barrier in Sam's mind to protect him from the memories of Hell, but it may not be permanent. As the season progresses we find out that Castiel has made a deal with Crowley, the King of Hell, to go after all of the souls in Purgatory so that he will have the power to defeat the Archangel Raphael. When the boys find this out, it is revealed that Castiel is the one who brought back Sam, and they attempt to talk Castiel out of his plan, but his mind is made up. This creates a rift between Castiel and the boys. In order to make the boys back off, he breaks the wall in Sam's mind, releasing all of the blocked memories. The season ends with Castiel successfully opening the door to Purgatory and swallowing all of the souls within. This makes his power overwhelming and he declares himself the new God.
*In this show, Purgatory is where all of the creatures go when they are killed, such as vampires, werewolves, etc.