'Supernatural' Season 10 Spoilers: Will Dean Kill His Brother Sam?

Episode 18 of "Supernatural" Season 10, entitled "Book of the Damned," will see Charlie fulfilling her promise to the Winchester brothers to help in their effort to find the Book of the Dead. The episode will on April 15, 2015 on The CW.

According to the episode's official synopsis, Charlie will call Sam and Dean to tell them that she have found the Book of the Dead which could help remove the Mark of Cain.

The brothers will try to reach her quickly after she tells them she's been shot by a man named Jacob Styne who says the book belongs to his family and that he won't rest until he gets it back.

Meanwhile, Castiel and Metatron go on a road trip to find Castiel's grace, but they hit some road bumps along the way.

Actor Jared Padalecki, who plays Sam Winchester, told the audience at Seattle's Salute to Supernatural that the "final episodes are very traumatic."

As Dean's condition worsens, Castiel and Sam will stop at nothing to find a cure.

However, will the cure involve Dean (Jensen Ackles) killing Sam, as it was noted that the only way the Winchester can be cured is by killing his own brother?

Cain revealed his protégé is living his life in reverse. Cain's journey started when he killed his brother Abel. Dean's final step in his journey might be killing Sam.

Sam opened the season with a vicious determination to locate a missing black-eyed Dean, and the possibility of seeing the elder Winchester turn once more will apparently bring out that vein of darkness again. "Sam does have a lot of darkness in him, so does Dean. I think it's one of the themes that, as long as Supernatural is alive, that theme is going to be around. Both of these guys are struggling with their demons, struggling with their past," Padalecki said in the same Seattle event.

"I think we will see Sam get dark. I know we do a little bit this season that you haven't seen yet. So I think you'll see it from Sam and Dean both."

"We are filming the final arc of Season 10 right now, and it's one of those really intense final arcs, I mean it's probably the most intense I can remember since like Season Five or something like that," Padalecki said while in Seattle.