Sam and Dean are ambushed by Meg the demon and some of her followers loyal to Lucifer, who are running from Crowley. Sam proposes a bargain: Meg will get to kill Crowley, if she can help them eventually recover Sam's soul. Meg agrees, and Sam decides to seek insurance in case of treachery. They try to get assistance from Samuel, who refuses - Crowley has promised to resurrect Sam and Dean's mother. Later, Samuel appears to have a change of heart, and tells the brothers and Castiel about a hidden monster prison Crowley is running, torturing creatures for information on Purgatory. During their preparation to attack the compound, Castiel voices his concern that since Sam's soul was locked with the very angry Michael and Lucifer, the ravages upon Sam's soul would either kill him or render him insane or broken. While attempting to infiltrate the compound, Meg's demons are killed by a hellhound, and Meg fights the creatures to buy the others time. Samuel has betrayed the brothers, forcing Castiel out of the building with a sigil spell and trapping Sam and Dean with Crowley's help. Sam escapes his guards, rescues Dean by killing the pair of ghouls, then Dean kills the demon controlling Christian, who found Meg and was torturing her for information. Together, the group tricks Crowley into stepping into a devil's trap, where Crowley states that getting the soul would be impossible, even for him. Crowley frees himself from the trap when Meg attacks him. Castiel reappears with Crowley's remains in tow, and once again Crowley professes that he cannot get Sam's soul back. Castiel immediately sets the bones ablaze, killing Crowley. Meg quickly vanishes, and Castiel leaves to fight a losing war against Raphael. Sam walks away from Dean stating that he doesn't want his soul back, as he is better off without it.
Source: Wikipedia
Source: Wikipedia