"Supernatural" Season 11 Spoilers
The Winchester brothers will notice something strange about their friend Castiel (Misha Collins) during Season 11, episode 11 of "Supernatural." The CW

The Winchester brothers may have gotten the “hell out of hell” but that doesn’t mean their dance with the devil is over. When episode 11 of “Supernatural,” titled “Into The Mystic,” airs, Sam (Jared Padalecki) and Dean (Jensen Ackles) will come face-to-face with Lucifer (Mark Pellegrino) … without even knowing it.

In the Season 11 winter premiere, the fallen angel slipped under Castiel’s (Misha Collins) skin, using Cas as a vessel to take on The Darkness (Emily Swallow). According to Lucifer, he’s the only one powerful enough to end Amara’s reign of terror — only so that he can begin his own.

During the upcoming episode, the boys will sense that there is something different about their longtime friend (whose body is currently being inhibited by a “neck snapping, cash checking” creature).

“Cas … something’s off about him,” Dean correctly assumes.

“Keep an eye on him,” Sam replies.

But, according to episode 11’s synopsis, babysitting Cas may be harder than anticipated when the duo receives an alarming call.

“Sam and Dean will investigate a case where people are suffering violent deaths after hearing a mysterious song,” the summary reveals. (And considering the episode is named after Van Morrison’s hit song, we really hope this episode won’t give us nightmares after listening to Morrison’s 1970 album “Moondance.”)

Viewers get a peek at just how vicious the deaths are when the promo for the upcoming episode showed a man falling out of a window to his death. But that wasn’t the only thing giving audiences goose bumps. A creepy, dark creature appears in the video, scaring characters with its impeccable force and odd, alien-like body. (Is it possible that mysterious being is Amara?)

“Supernatural” Season 11, episode 11 will air on Wednesday, Jan. 27, at 9 p.m. EST on the CW.