'Supernatural' Midseason Finale Spoilers: Mark of Cain to Drive a Wedge between Sam and Dean?

There's just one more episode to go before the midseason finale of "Supernatural" airs on 9 December, and speculations are rife that the dark side of the eldest Winchester brother, Dean, will once again become prominent.

Dean was turned into a demon in the finale of the previous season after he was killed by Metatron. And although season 10 was promised to be a "year of Deanmon," fans were left disappointed when Dean was finally cured in the third episode. Now, everything between the two brothers seems fine, but it won't be long before the Mark drives a wedge between Sam and Dean, spoilers tease.

The synopsis of the episode titled "The Things We Left Behind" does not reveal much about what will be in the midseason finale. However, it does note that Castiel will turn to Sam and Dean to track down Jimmy's daughter Claire, and that Crowley will face his biggest challenge yet.

But the effect of the Mark of Cain on Dean is going to get sufficient screen-time, according to spoilers.

"You're going to see Dean dealing with this pretty much for the next chunk of the season, as he and Sam take different paths in how to deal with it," executive producer Jeremy Carver teased to TVLine earlier. "While we're all very happy he was cured of being a demon, there's a lot more work to be done."

As for what to expect in the finale, actor Misha Collins, who essays the role of angel Castiel in the series, teased that the primary plotline of the mid-season finale will focus on his character.

"It's going to be a great little arc. I don't even know how little the arc is or how big it is. We, so far, are doing two episodes that focus [on Claire.] It's the midseason finale and midseason premiere," Collins told SheKnows.

As fans of "Supernatural" know, Claire is the daughter of Castiel's vessel, Jimmy Novack, and the mid-season finale and premiere will focus on the father-daughter relationship.

Meanwhile, the next episode is titled "Hibbing 911" and it is the eight episode of season 10. The episode will air on 2 December and it will see the return of Jody Mills (guest star Kim Rhodes).

According to the synopsis,"Jody Mills reluctantly attends a mandatory sheriff's retreat and is partnered with an overeager sheriff named Donna (guest star Briana Buckmaster) who wants to bond. Just as Jody thinks things can't get any worse, a body with just strings of meat and skin hanging off the bones is discovered. While the local sheriffs blame an animal attack, Jody knows better and calls Sam (Jared Padalecki) and Dean (Jensen Ackles)."