'Supernatural' season 12 episode 12 spoilers: Mary's new mission puts Castiel's life in danger; 'long-forgotten Lucifer lore' to be explored

Mary (guest star Samantha Smith) works for the British Men of Letters on the upcoming episode of The CW's "Supernatural" season 12.

Titled "Stuck in the Middle (With You)," next week's episode will feature Mary's new mission that puts her at odds with her sons. According to the official synopsis, Mary works on a new case, and she will seek help from Sam (Jared Padalecki), Dean (Jensen Ackles), and their angel friend, Castiel (Misha Collins). However, she fails to tell them that the British Men of Letters are involved. The organization eventually double crosses Mary, and everything will be revealed.

The CW released a new promo for the upcoming episode, hinting that Castiel's life might be in serious danger. The clip shows a bruised and bloodied Castiel dragging his own body. "Please, please don't let my last moments be spent watching you die. Just run," Castiel tells Sam and Dean. Some of the scenes feature Mary and her sons fighting a number of bad guys as well. It remains to be seen if Castiel survives, but Sam and Dean will certainly do everything they can to save their good friend.

Aside from Mary's new mission, episode 12 will also explore the Lucifer story arc now that his child has arrived on Earth. It is expected that his presence will be felt even more as the series moves forward.

"I think the fact that he's got a kid rolling around out there, he's not dead," showrunner Andrew Dabb told Entertainment Weekly. "I think we're dealing with a world where even if Lucifer is off the table in some ways, his influence will still be felt. In episode 12, we're introducing a fun extension of our mythology. Some long-forgotten Lucifer lore may come out of the woodwork now that his kid is kind of up for grabs," he went on to say.

The 12th season of "Supernatural" airs every Thursday night at 8 p.m. ET on The CW.