Enjoying his time as a demon and killing several of Abaddon's loyalists, Dean eventually kills an man called Lester Morris and uses his newfound demon powers to confirm what Crowley told him about Sam. Eventually confronting his brother, Dean is pulled into a fight by a soldier named Cole, allowing Sam to use holy water to imprison his brother. Using the demon cure process to try to turn his brother back, Sam lets his guard down and Dean escapes. With the help of Castiel, however, Dean is cured, but still remains an enhanced human with the Mark of Cain. After eventually growing more and more powerful while losing control, Dean learns from Cain, before killing his ancestor, that there is no viable cure. Death later confirms this by revealing that removing the Mark would unleash the Darkness and offers to remove Dean from society on the condition that he kill Sam. Although he initially agrees, Dean relents and kills Death instead. However, due to Sam's earlier machinations, the Mark is removed and the Darkness is unleashed regardless.