Season 10 of "Supernatural" is going to be full of twists and turns, with Sam in search of his brother Dean, who turned into a demon at the end of season nine, and Castiel's failing grace making him a mortal being, the official synopsis of the upcoming season stated.

When the next season airs in October, Dean will be shown as missing. But it is not immediately known if Sam is aware that his brother has been turned into something that both of them despise.

Based on a tweet by John Bring, a writer's assistant at "Supernatural," Dean will be a scary demon, who is out to do some serious damage.

"I can't wait to see Jensen kill it as demon Dean," Bring reportedly wrote on his Twitter account. "He's gonna be one scary sonofab*tch."

Jensen Ackles, who plays Dean in the series, spoke about the future of his character stating that the Mark of Cain will make him more powerful than an average demon.

"It's interesting because there are a few aspects to what could potentially be Demon Dean," Ackles explained at Rome's fifth annual Jus In Bello Convention, according to Enstarz.

"You've got to think about the fact that he's got the Mark of Cain as well. So you look back at what that was for Cain and the power that he had against other demons. So is Dean going to be this ultra-powerful demon, and therefore be ultra bad? I don't know. I will say that I'm looking forward to exploring what that means and where that's going to take the story," he added.

Reports have it that Dean will also have a new love interest in the upcoming season. A roadhouse cocktail waitress named Ann Marie will catch his fancy, and the demonic Dean will prove that he is not without a heart. It remains to be seen if their relationship will turn serious, but an "intense fling" is guaranteed, according to TV Line.

Another female character that will be introduced in season 10 is Rowena, who is believed to be a tough but elegant woman who will stop at nothing to reclaim her power.

"Season 10 begins with Sam's frantic search for his missing brother, who is gone without a trace. The road to recovering the wayward Dean takes Sam down dark paths, with consequences that will shake the boys to their core," the official synopsis reads.

Meanwhile, Castiel will be dealing with the aftermath of Metatron's campaign. The presence of a number of rogue angels on the loose does not make his job easy.

"Supernatural" Season 10 is scheduled to premiere on Oct. 7 at 9 pm ET on The CW Network.