After the midseason finale of Supernatural season 10, Dean's condition seems to have escalated from just being affected with the Mark of Cain, to the mark taking over his body.
Executive producer Jeremy Carver has revealed that Cain (Tim Omundson) will return to the show and will shed light on the Mark of Cain and what it means for Dean.
Carver told E!Online: "Dean's interaction with Cain will have a profound effect on Dean, how he thinks about the mark, and how he thinks about himself with the mark."
"It's a pretty wonderful episode and what it means for the season-long arc is pretty dramatic. We're excited about this episode," he added.
The producer also talks about the immediate concerns for Sam (Jared Padalecki) and Castiel (Misha Collins), on how the Mark of Cain is affecting Dean's actions.
"Everyone's pretty shell-shocked by it. As concerned as they are with Dean's welfare, there are even bigger concerns as to how they can stop this from happening again," Carver said, adding, "That's really going to drive our guys to the end of the season, dealing with the Mark and trying to prevent this from happening again."
Carver also pointed out that the Winchester brothers will have to deal with people they would rather not want to associate with. "All of this is going to make them ask some very hard questions as the season goes on," he adds.
But unlike previously, Dean will not push Sam away during the testing times ahead.
"It's going to be a little bit of both allowing Sam to help and taking it on himself," Carver explained.
"The boys are going to be open with each other and not open with each other at the same time when it comes to the Mark. Dean's not going to completely admit how it bothers him sometimes, but Sam is not a dummy. He knows how it's affecting Dean now, but then again, he might not always say how he knows it's affecting Dean. It's the elephant in the room as the season heads to the end," he concluded.