Season 10 of “Supernatural” is winding down, which means fans of the hit CW series should start preparing themselves for an action-packed -- and dare we say, emotional -- finale. According to the synopsis for “Brother’s Keeper,” Dean (Jensen Ackles) will leave audiences with their mouths agape when he makes a shocking decision that not only effects his fate, but the life of Sam (Jared Padalecki), too.

For the past season, Dean has struggled with the destructive Mark of Cain. And while Sam believes his older brother can still be saved from the soul-sucking curse, Dean has come to terms with the fact “that there’s no way” he can be saved.

“Instead of forcing his support group of Sam and Castiel (Misha Collins) and Charlie (Felicia Day) to help a helpless cause, it just seems fruitless to him, so he basically says ‘guys, stop, leave it alone, there’s nothing you can do, and there’s nothing I can do except fight until I can’t fight anymore,'” Ackles revealed to Variety when speaking on why his character has given up hope. “And unfortunately, we’re gonna see what that means in the last episode.”

Although Dean has lost his lust to fight, Sam will zealously try to find an antidote for his brother -- even if it kills him.

“Sam can’t find a cure, and of course, the loyal brother that Sam is will die trying, and Dean knows this,” Ackles said.

The actor then divulged to Variety that the conflict in the finale is an internal one. “It’s not something that they can lock and load their shotguns and go after together,” he stated, adding, “It really is this inner struggle where Dean can’t seem to get a grasp on the evil power that’s inside him, and Sam can’t seem to let go of trying to save his brother.”

Ackles elaborated that the battle will come to a head at the end of the season, which will air on Wednesday, May 20. “It’s a good one,” he teased when discussing just how exciting the Season 10 finale will be. “In fact, in my opinion, I read the script and I’m like, ‘this is one of the best scripts I’ve read in years.”

However, episode 23 has one cast member feeling a bit queasy. Collins revealed that in a last attempt to save Dean, a deal with the devil will be made. And of course a contract of that stature will require an “enormous sacrifice.”

Collins explained that there was a moment in the last episode (when they are making the sacrifice) that had him thinking, “‘How are our characters okay with this? This is terrible, what we’re doing. This is disgusting.’ We’re making some serious compromises in order to rescue Dean.”

This wouldn’t be the first time morals were broken to save the black-eyed Winchester. In the Season 10 premiere of "Supernatural,” fans watched as sweet, little Sam tortured a demon to find out his brother’s whereabouts.

"Whatever soul you had, whatever Boy Scout code you cuddled up to at night, it’s all gone,” the demon said, revealing Dean wasn’t the only wicked Winchester wreaking havoc.

What do you think will happen in the Season 10 finale of “Supernatural”? Sound off in the comments section below with your theories and don’t forget to tune in to “Supernatural” on Wednesday nights at 9 p.m. EDT on The CW.