'Vampire Diaries' season 8 spoilers, plot latest news: Stefan's dark streak continues as Damon finds a breakthrough against Sybil

After Stefan joined his brother Damon in the dark side at the end of the midseason finale of "The Vampire Diaries" season 8, the Salvatore brothers are expected to cause chaos in Mystic Falls when the series returns early next year.

In the previous episode titled "The Next Time I Hurt Somebody, It Could Be You," Damon brought Cade (Wolé Parks) with him when he dropped by the holiday celebration of Stefan and his fiancée Caroline (Candice King). Instead of having a fun-filled celebration, Cade ruined the holiday dinner that Stefan had long been planning for when he made him remember all the terrible things that he did in the past, including the Christmas murder in Monterey back in 1917.

After their chat, Stefan decided to take on Cade's offer to be his ripper for a year in exchange for his and Damon's freedom after his tasks are done. But to be able to be effective in his role, Stefan must turn off his humanity.

Based on the trailer for the upcoming episode titled "We Have History Together," the Salvatore brothers will continue with their evil tasks under the influence of Cade. But Damon might finally make a breakthrough against Sybil (Nathalie Kelley) in the second half of "The Vampire Diaries" season 8.

Meanwhile, the rumored return of former female lead Nina Dobrev continues to be talked about online, especially since Georgie's (Allison Scagliotti) death reminded fans about Katherine's (Dobrev) death in the past.

In an interview with Entertainment Weekly in November, showrunner Julie Plec opted not to give a concrete answer about Dobrev's possible return in the show. "I will confirm nothing, but the visual similarities are not accidental," the showrunner stated. This means that the scene is paving a way for a big surprise before the series airs its last episode next year.

The eighth and final season of "The Vampire Diaries" will return on The CW on Friday, Jan. 13.