The Winchesters have - once again - gone their separate ways. While Sam has remained at The Bunker with Cas to continue the healing process, Dean has gone off in pursuit of Abaddon - only to find himself forming an unlikely partnership with Crowley.
Cas discovers an element of Gadreel's grace left in Sam and explains that it could be used to track down the errant angel, if it can be extracted (a painful process involving a giant needle!)
Meanwhile, via one of John Winchester's old contacts, Dean and Crowley are on the trail of the First Blade, a mystical weapon believed to be powerful enough to slay a knight of Hell (i.e. Abaddon).
Their quest takes them to Cain (Timothy Omundson) - as in "...and Abel" - who Dean learns is actually a mighty demon, responsible for forming, and training, the knights of Hell.
He has, however, retired and ants nothing to do with Dean and Crowley. Unfortunately, the situation quickly worsens when they realise they have been followed by demons working for Abaddon.
Initially, First Born felt almost like a filler episode, but gradually its importance is made manifest as the two distinct plot threads unfold.
I can't even begin toe guess where Sam's story is heading at the moment, but Dean's - given what happens to him at the end of this episode - is clearly heading for a very dark place.
The episode also gave us a clever twist on the traditional interpretation of the story of Cain and Abe, proving once again that the ever-growing Supernatural mythology is flexible enough to accommodate a wide variety of stories.