To what extent Alastair has something to do with Dean's life is revealed in the new sneak peek released by The CW. Next week on "Supernatural", Dean is sent by Castiel and Uriel to use his torturing skill he learned in Hell to extract information from Alastair but the demon reveals some shocking revelations that shatter Dean's world.
In "On the Head of a Pin", someone found Lucifer's sword and is using it to kill angels. Castiel and Uriel have captured Alastair and ask Dean to question him so they can stop the murders. Sam is concerned Dean can't handle the job but Dean agrees to do it. However, Alastair revealed that he had done something to Dean's father in the past.
"On the Head of a Pin" airs March 19.