Despite his brother's orders to the contrary, hunter Sam Winchester chooses not to destroy the Book of the Damned, seeing it as his best shot for removing the Mark of Cain from Dean's arm before it turns Dean into a monster. As the Book of the Damned is in code, Sam begins putting a team together to decode and use it to remove the Mark of Cain from Dean.
Believing that the powerful witch Rowena MacLeod could likely read and use the Book of the Damned, Sam sets up a meeting with her to negotiate Rowena's help. In exchange for Sam killing her son Crowley, Rowena agrees to help Sam out. However, Rowena is unable to begin right away as even she can't read the Book of the Damned. Rowena informs Sam that he must first find Nadia's Codex which can be used to decode the Book of the Damned.
With the help of an oblivious Dean, Sam is able to disarm the Werther Box where the codex is located and retrieve it. Sam brings the codex to Rowena who confirms that she can use it to decode the Book of the Damned. To ensure Rowena's compliance, Sam binds her in iron chains, promising that he will kill Crowley as promised once the Mark of Cain is removed from Dean's arm but Rowena will not be allowed to keep the Book of the Damned or the codex.
After days of Rowena coming up with nothing, Sam learns that the codex is also coded and must first be decrypted itself before it can be used to read the Book of the Damned. In order to keep the continuing work a secret from Dean and to speed up the process, Sam calls in the hacker and hunter Charlie Bradbury to use her tech skills to help crack the code. Sam fleshes out the team further by bringing in the Seraphim Castiel to act as protection and to ensure that Rowena remains guarded and on task.
Even with Charlie's computer expertise, there are problems with the decryption. The newly-formed team also faces internal strife due to the differences of opinion between Charlie and Rowena which leads to a good deal of bickering between the two. Desperate to get some peace and quiet, Charlie slips away to the Blackbird Motel where she is eventually able to create a decoder for Nadia's Codex and through it, the Book of the Damned. Moments after creating her decoder, Charlie comes under attack by Eldon Frankenstein of the Styne Family who is looking for the Book of the Damned. To keep Eldon from getting her decoder, Charlie destroys her Surface Tablet, but not before emailing the decoder to Sam. Shortly thereafter, Charlie is murdered by Eldon.
Having learned of the team's efforts, an enraged Dean orders Sam to disband the team and stop their work. Heartbroken over Charlie's loss and believing it to have all been for nothing, Sam decides to comply and states his intention to kill Rowena to Castiel. However, Sam receives Charlie's email with her decoder which Rowena confirms can be used to crack the Book of the Damned. Sam decides to press on to save Dean, but Rowena forces Sam to kill Crowley and hold up his end of the deal before she will remove the Mark of Cain. Sam ambushes Crowley, but fails to kill him and Rowena demands that he needs to keep trying.
With Dean's condition growing worse, Sam creates witch-killing bullets in an attempt to threaten Rowena into completing her task. Rowena recognizes the bluff for what it is, but agrees to perform the spell in exchange for her freedom and Nadia's Codex. Sam reluctantly agrees to the new deal and Rowena deciphers the needed spell ingredients for the Mark of Cain Removal Spell. Getting a call from Rudy about Dean's behavior, Sam leaves to find his brother while leaving Castiel and Rowena to complete the task.
In order to get the ingredients, Castiel summons Crowley for help. After seeing the list, Crowley agrees to sign on with the effort and is able to retrieve the needed ingredients, including a young man named Oskar that Rowena had made immortal three hundred years before. Rowena is forced to sacrifice Oskar, but completes the spell, removing the Mark of Cain from Dean's arm and completing the team's task. However, the Mark of Cain's removal triggers the release of the Darkness.
The shockwave from the spell frees Rowena from her chains and she departs with the Book of the Damned, Nadia's Codex and Charlie's decoder. As she leaves, Rowena sets Castiel upon Crowley in a failed attempt to kill her son.
- Sam Winchester (founder and leader)
- Rowena MacLeod (team's witch)
- Charlie Bradbury (second in command and team's hacker, deceased)
- Castiel (team's enforcer)
- Crowley (team's supplier, deceased)