Captives had two distinct threads to it, neither overlapping, yet both serving the main season arc in their own way.
In one plotline, Sam and Dean are contacted by the ghost of Kevin and told that not only is Heaven closed to new admissions since the fall of the angels but also that he learned, through another spirit trapped in "The Veil", that his mother was actually still alive.
The Winchesters head to Wichita to contact this other spirit, a woman called Candy (Lina Roessler), who explains that she and Kevin's mother were being held prisoner in a storage unit.
The brothers realise that Crowley had been holding them as blackmail assets and so set about finding Linda Tran (Lauren Tom) before anything happens to her.
Meanwhile, the other plot thread sees Castiel captured by Bartholomew's (Adam J. Harrington) angelic host - with the aim of convincing him to join their side in the on-going civil war.
It turns out that Bartholomew had served under Castiel in Heaven and he was hoping to persuade his old boss that united they could bring an end to the war and restore order to Heaven.
Things don't exactly go as planned and by the end of the episode, Castiel finds himself in an uncomfortable new position that he never sought.
Captives was a fine, workman-like episode that had a job to do and did it well. The Winchester brothers are still at odds with each other and even Kevin's words of wisdom fall on deaf ears, but at least Kevin's story appears to have reached a satisfactory conclusion and the brothers have learned a bit more about what's going on in Heaven.
Although it was clearly the secondary plot, the developments in Castiel's life are definitely the most interesting in respect to the season arc and, as ever, it will be great to see where the writers take this fan-favourite character next.