Supernatural Season 6 Episode 18 (04/22/11)
On this week's episode of Supernatural...
Sam and Dean discover that a Phoenix's ashes can kill the Mother of All.
Castiel uses his powers to send the boys back in time to the Old West in order to find Samuel Colt and gather the ashes.
They encounter a phoenix on a vendetta because his wife was murdered.
Sam confronts Samuel who claims he quit hunting. Rather than travel with Sam, he gives him his gun. Dean uses the gun in a showdown with the phoenix.
After Castiel's own showdown with the angel, Rachel, he uses Bobby's soul to power himself and retrieve the boys from the past. Dean fails to collect the ashes, but a package is delivered from Samuel Colt in the present. It contains the ashes.