Supernatural Season 10 returns with its mid-season finale episode tonight, 9<sup>th December at 9:00 pm on The CW.

Episode 10 is titled, The Things We Left Behind, which might bring back Demon Dean to the show.

Click here to watch the episode online.

The official synopsis reads:

Castiel (Misha Collins) finds Jimmy's daughter Claire (guest star Kathyrn Love Newton) in a group home and she convinces him to break her out. After she runs away from him, Castiel calls Sam (Jared Padalecki) and Dean (Jensen Ackles) to help find her before she gets in trouble. Meanwhile, Crowley (Mark A. Sheppard) faces his biggest challenge yet.

In the last episode, we saw the Winchester brother dig around in folklore to get rid of The Mark of Cain on Dean's hand, with no success.

But, going by the promos for the mid-season finale, Dean will give in to his dark side and might become the Knight of Hell again.

The promo also shows Dean asking Castiel to take him down, if he ever becomes Demon again.

"I cant go down that road again.. I can't be that thing again," says Dean.

Watch the promo and sneak-peek here: