Supernatural's Sam Winchester would like nothing more than to restore his brother's humanity, but Demon Dean's Mark of Cain will make this task more difficult than either hunter could have imagined.

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Dean (Jensen Ackles) is no ordinary demon. Extraordinarily powerful and not possessed, this new monster is like nothing the brothers have ever encountered.

"They're going to see new difficulties in trying to cure Dean, because 1) There's not a demon possessing Dean. This is Dean's own soul that was twisted, so that's a bit unique," explained executive producer Jeremy Carver, according to Entertainment Weekly. "And 2) It's not just the demon-ness that's the problem, it's the Mark of Cain. So there's some added dimensions here in terms of levels of difficulty."

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Figuring out how to remove the Mark - and if it can be removed - will be one of the major problems for the Winchesters. If the Mark doesn't need to be removed in order to restore Dean to the land of the living, it will continue to cause issues as the season progresses.

"It's still around, and it's very much a question for the first run of episodes if it still has an effect on Dean or not," Carver continued. "And it's very much on the boys' minds as they plot out a game plan for the next batch of episodes after Dean is healed."

Find out more when Supernatural returns to The CW on Oct. 7 at 9 p.m. ET.