The midseason finale of “The Vampire Diaries” aired on Thursday, and didn’t disappoint. Find out what happened in episode 10, “Fifty Shades of Grayson”:

Damon managed to break out of the cell that Dr. Wes locked him in and returned to his house to ask Stefan for help in finding Elena. But when Damon returned to the old Salvatore boarding house, he discovered more than his brother – he found a feisty Katherine.

“We were together all night,” she tells her ex of her hot tryst in the sheets with Stefan.

“I’m gonna barf,” Damon counters. “Ugh.”

Choosing to ignore Katherine’s disturbing revelation, Damon recruits Stefan to help find Elena, and the pair head to Whitmore College to find leverage … Aaron, to be exact. Getting their hands on Elena’s former friend, Damon and Stefan force him to call Dr. Wes, his legal guardian. But unfortunately for Aaron, Dr. Wes doesn’t want to play by Damon and Stefan’s rules. Instead of offering Elena in exchange for Aaron as he promised, Wes decides to send Enzo to wrap up his unfinished business with Damon.

While Damon and Stefan wait for Dr. Wes, he’s busy in Grayson Gilbert’s former clinic basement … draining Elena of her blood. Strapped to a table, Elena begins to learn the shocking truth about her father. It turns out that he was conducting experiments like electrocuting vampires with high voltage in the basement of his Mystic Falls practice. He had been conducting gruesome experiments and hiding it from his family for years and seemingly up until his death.

“Everything I’m doing to you I learned from him,” Wes tells Elena.

But that’s not all Wes reveals. The cruel doctor also unveils the identity of Megan’s killer, the Augustine vampire – Enzo. Megan’s parents had helped fund Gilbert’s experiments after he saved 7-year-old Megan’s life. Megan got suspicious of the “un-regulated compound” that cured her and went digging around the Whitmore house, where she found Enzo locked up. Dr. Wes believes that Megan got too close and a hungry Enzo fed on her.

As Elena gets weaker, Enzo comes face-to-face with Damon after 60 years. And needless to say, the Augustine vampire is none too pleased with Damon.  

Enzo explains that on the night of Damon’s betrayal he was saved by one of the Whitmore scientists. Dr. Wes only let him out of his cell today after injecting him with poison and telling him the only way he would get the cure was if he killed Damon.

Damon’s left alone with crazy Enzo as Aaron takes Stefan to his dorm with the promise of files that could potentially reveal where Dr. Wes is keeping Elena hidden. But Stefan gets more than the files – he learns of Damon’s sick plan of revenge that he’s been working on for the past 60 years.

Figuring out that Elena is at her dad’s old office, Stefan rushes in just as Wes stabs her with his latest creation – a shot that will force her to thirst for only vampire blood. Wes manages to stick her with the needle, but a head-butt from Elena causes him to drop it before injecting her.

As Stefan rescues Elena and takes her home, Damon is forced to fight a poisoned Enzo. Trying to convince his old friend to team up and go back together to “finish this for good,” Enzo refuses … but shortly after collapses from the poison. Fortunately for Enzo, Damon would not give up on Enzo a second time and manages to find the anecdote for his poison.

While Damon, Stefan and Elena deal with the Augustine situation, Katherine reunites with Nadia, who has an offer that could potentially keep Katherine alive for longer. “Vampire Diaries” fans will remember that Katherine and Nadia come from a long line of travelers. Nadia suggests that they use one of the old traveler spells to turn Katherine into a passenger of another body. And although it seems like a good idea, Nadia changes her mind and tells her mom to “go kill herself” when she realizes that Katherine is only trying to stay alive for Stefan.

Unfortunately “The Vampire Diaries” didn’t have a happy ending for its midseason finale:

-Nadia decides to leave town and asks Matt to hold onto the traveler’s knife – the piece needed if Katherine changes her mind about becoming a passenger.

-Damon breaks up with Elena despite her confessing her love for him (again). “I’m bad, Elena,” he tells her. “I’m bad for you … I’m choosing to let you go. I’m choosing to relieve you of having to defend me of every awful thing you’ve ever done.”

- Stefan tells Katherine that their hookup wasn’t anything special the night before and that he can’t just forgive her overnight for 147 years of torture. “It was a long day,” he explains. “We had a moment and we got swept up in it.”

-Aaron confronts Dr. Wes and tells him that he never wants to see him again. But before he leaves he picks up the loaded syringe and walks out.

-Katherine calls Nadia and asks to become a passenger, but before they can finish their conversation Katherine collapses of a heart attack.

Do you think Katherine really died? Let us know your thoughts on episode 10 of “The Vampire Diaries” in the comments section.