Things are turning darker in the world of the Winchester brothers as Dean (Jensen Ackles) continues to wreak havoc due to the effects of the Mark of Cain on his body, which will be seen on the 10th episode of "Supernatural" season 10. 

In the upcoming episode titled "The Hunter Games," Dean will be on a murderous streak. He mercilessly slays Claire's partner Randy, the loan shark who Randy is indebted to, and the loan shark's men, inside the home of one of his victims. His younger brother Sam (Jared Padalecki), their friend Castiel (Misha Collins), as well as Claire, witness his horrible deed, prompting them to look for ways to help him get rid of his highly dangerous new persona. 

Before he became widely consumed by the Mark of Cain, Dean already gave an instruction to Castiel to do whatever is necessary so that he would not return to his evil, demonic personality. The angel tried to ask the Men of Letters for help in removing the Mark of Cain from the older Winchester brother, but his efforts failed. He's trying to come up with another plan but Sam strongly opposes it, saying that it's the stupidest idea that the angel could think of. 

Will Castiel and Sam successfully help Dean remove the Mark of Cain? 

Meanwhile, a returning character will visit the show in the coming episodes. According to earlier spoilers, Charlie (Felicia Day) will return to find the Winchester boys, but her visit will not be a peaceful one. "Supernatural" co-executive producer Robbie Thompson shared a few teasers about Charlie's visit in his interview with TVLine.

According to Thompson, Charlie "brought something back that's very dangerous. She teams up with the boys to track that dangerous thing down and hunt with them, basically." 

Will Dean be able to help Charlie find what she is looking for in his current state?

"Supernatural" season 10 episode 10 airs on The CW on Jan. 20.