Sam and Dean learn that Cain has kidnapped a serial killer named Tommy Tolliver while at the same time, Castiel discovers a graveyard full of Cain's victims. Cain confronts Castiel, revealing that he has fallen back under the influence of theMark of Cainand is now slaughtering his descendants, thinking his bloodline is tainted. In order to stop Cain, Dean calls upon Crowley to give him the First Blade, lying to him that Cain wants Crowley dead. As a result, Crowley blows off his mother Rowena's wish to kill a witch of the Grand Coven to help the Winchesters. Working together, the four trap Cain in a devil's trap when he arrives to kill his next victim, a twelve-year-old boy. Dean confronts Cain alone who tells him there is no cure for the Mark of Cain, and it's just better to give into its power. Dean and Cain fight, but Dean loses as he holds back in fear of losing his humanity. However, he eventually manages to get the upper hand and asks if Cain will give up killing again. Upon Cain's declaration that he won't, Dean kills him, devastated by the fact that there seems to be no way out for him. Despite his fears, Dean manages to keep control of himself, but gives Castiel the First Blade instead of Crowley as he promised, shocking Crowley with his lies. Rowena later tells Crowley that he's not a king anymore and is nothing but the Winchesters' lap dog. Sam expresses the belief that if Dean could kill Cain himself without losing his humanity there is still hope for him, while he privately tells Castiel and bella that Dean's in trouble.