Lucifer's words have wormed their way into Sam's head, making him doubt himself, but Dean finds a local case for them, a locked room murder at an old folks' home.
At first they reckon it's a run-of-the-mill vengeful spirit that can be beaten with the classic "salt and burn the bones". However, a second murder dispels that theory and leads them to believe it's a malevolent banshee, preying on the vulnerable.
Teaming up with Eileen Leahy (Shoshannah Stern), a freelance hunter who has been tracking the banshee, and with the assistance of Mildred Baker (the ageless Dee Wallace, star of E.T., The Howling, Cujo etc), the feisty and flirtatious resident they believe is going to be the next target, the brothers set a trap for the monster.
Meanwhile Lucifer is walking around in Castiel's body (major props to Misha Collins for his portrayal of the possessed angel), supposedly looking for a spell that could take down Amara, but also talking Dean into opening up about his 'connection' to The Darkness.
Into The Mystic was a superb episode, that cleverly interwove a real old school "monster-of-the-week" episode with major threads from the season's overarching plotline.
Even though the CGI monster wasn't one of the show's finest, the lore developed around the creature is so deep that it makes the episode's antagonist fascinating enough that you can look past the not-so-special effects.
The balance between levity and the violence of the banshee's attacks in Into The Mystic was also handled deftly, particularly Mildred's cougar-esque advances on Dean, who was clearly flattered and, probably, slightly tempted because of his professed attraction to Blanche from The Golden Girls!
And, if you've been following my Supernatural reviews, you'll know I always welcome new additions to the core family of characters, so I was delighted by the introduction of Eileen and very pleased to see that this new hunter survived to the end of the story, with the door left open for her to return at a later date.