The Winchester brothers, who are the main characters of the television show Supernatural, have only one goal throughout the show. That is to help Dean get rid of the Mark of Cain, which has been haunting him for his entire life. However, just as the treatment to his problem has been found, a plot twist has come up to interfere.

The latest episode of Supernatural, which is called "Book of the Damned," features Charlie telling Dean and Sam that she has finally found the Book of the Dead, which is the key to helping to free Dean for the Mark of Cain.

The evil effects of the Mark have done enough damage to his life already, and the group is excited to put a stop to it. However, as they find the book, Jacob Styne attempts to claim it, saying that it belongs to his family.

He even shoots Charlie in an attempt to retrieve the book. In the end, he tells Sam, Charlie and Dean that he will do everything that it is in his power to do so that he can attain the Book of the Dead.

Based on this, fans can assume that Sam and Dean's story and struggle will not end anytime in the near future. Jared Padalecki, the actor who plays Sam, hints at the fact that the show may take a darker turn for his character.

During the Supernatural Seattle Con, which took place recently, Padalecki said, "Sam does have a lot of darkness in him, so does Dean."

The actor also states that the theme of darkness will be present in the show as long as the Supernatural is alive.