Previously on 'The Vampire Diaries,' Elena was captured by the evil vampire-hating Dr. Maxfield. Will she survive her time on the table?

Back in Mystic Falls, Katherine wakes up next to sleeping Stefan, thrilled that she is once again cozying up to the youngest Salvatore brother. But Katherine's good time is ruined when she realizes that she has also woken up next to a clump of her own hair. We get it, Katherine, getting old totally sucks. Meanwhile, Damon, who has managed to unlock himself from his Augustine cell, heads to Mystic Falls, looking for Elena. He doesn't yet know that she has met the same fate as he did almost 60 years ago.

Elena's good doctor is performing a blood dialysis on the teen vampire, which, honestly, sounds a bit better than the whole "organ removal thing" Damon went through (and she even got anesthesia!). It's not only her physical body that is in pain -- Elena also has to deal with the fact that her own father tortured vampires, just as Dr. Maxfield is doing to her now.

Damon hits the college and finds Aaron, who is pretty shocked to find Damon not dead since he shot him in the heart in the last episode. Damon wrangles Stefan into helping him find Elena. Aaron calls his faux-Uncle and tells him that Damon and Stefan are going to kill him if he doesn't return Elena to him. Dr. Maxfield tells Aaron that he will return Elena. Of course, what Dr. Maxfield fails to mention is that he is bringing a certain friend of Damon's with him: Enzo, the vampire friend that Damon betrayed years earlier. Dr. Maxfield tells Enzo that he's getting the day off and throws him a bag of blood -- just the snack to fuel Enzo for this little reunion.

Meanwhile, Katherine is trying to turn back the hands of time the old fashioned way -- through diet and exercise at the hands of her personal trainer, Matt. Matt invites Nadia, Katherine's daughter, to hang out at the Salvatore mansion, where Katherine is spending her days drinking kale smoothies and pining over Stefan. Nadia is at first pissed that Katharine tried to kill herself, but decides to get over it when she sees how badly Katherine wants to live. Nadia tells Katherine that she has a way for Katherine to live longer. Little does Nadia know that the person Katherine wants to stay alive for is Stefan, not Nadia. Once an absentee mother, always an absentee mother.

Damon, Stefan and Aaron head to a lecture hall to meet up with Dr. Maxfield. But instead of Dr. Maxfield, it's Enzo sitting in the classroom. Enzo's introduction to Stefan and Aaron is pretty awkward, considering that Damon basically declines to apologize for his terribly unkind behavior years earlier. Even Stefan is alarmed by Damon's lack of remorse, and Damon actually stole his girlfriend. Damon tells Enzo that they need to work together to finish off the Augustine society, but Enzo isn't so into teaming up with Damon. Enzo hurls Damon through a window, pretty much telling him that, yes, he still does have some hard feelings about what Damon did to him.

A sedated Elena talks to Dr. Maxfield about her roommate, Meagan. It looks like Meagan wasn't quite as naive as she appeared -- she was killed by a vampire because she was suspicious about the secret lab in the Whitmore House. Unfortunately. she happened upon a pretty hungry Augustine vampire, and, well... bye bye, Meagan.

Back at the Salvatore mansion, Nadia tells Katherine that she can put her soul in a different body in order to save her soul after her body's death, since Katherine has the power of soul traveling inherited from her grandfather. But when Katherine tells Nadia that her real reason for wanting to stick around is Stefan, not Nadia, Nadia walks out, telling Katherine that jumping off the clock tower wasn't such a terrible idea after all.

Katherine isn't the only one not making friends. Damon and Enzo have the brawl to end all brawls. Apparently, Dr. Maxfield has poisoned Enzo, and will only let him have the antidote if he kills Damon. Enzo tries to do just that, but, unfortunately for him, the poison kills him before he can off his former friend.

Back in the lab, Dr. Maxfield is injecting Elena with the same chemical that he gave to Jesse, the hot-guy-turned-vampire who Elena killed in defense of Damon. The chemical will make Elena crave vampire blood: exactly what Dr. Maxfield wants. Dr. Maxfield injects Elena, but Stefan comes in just in time to save the day. He knocks Dr. Maxfield unconscious and carries Elena out of the lab. Elena grabs her father's notebook.

Nadia heads to the Mystic Grill to have a chat with Matt. She gives Matt the traveler's knife and tells him how sad she is that Katherine won't use it to live a little longer and spend time with her. Matt gets it -- his mom totally sucked, too.

Meanwhile, Damon gives Enzo the antidote that his body needs, and surprisingly, it works. Damon grabs Enzo's heart in order to have a literal "heart to heart" with his former buddy. He tells Enzo that he had to turn off his humanity in order to be able to leave Enzo in that burning building. Enzo tells Damon that no matter what he does, he will always have to live with being a terrible person. Damon reminds Enzo that they are even -- because now, Enzo can walk free. Sixty-plus years late, but I guess Enzo finally got the rescue he was looking for.

Back at the Salvatore mansion, Elena reads her father's journal and realizes that her father saved Elena's old roommate Meagan by using vampire blood to fix her heart defect. Damon tells Elena that she can find the good in anyone -- even him. Elena tells Damon that she forgives him for killing the Whitmore family, because she loves him and stands by her choice. Damon tells Elena that she needs to stop defending him -- he is bad for her. Damon tells Elena that he needs to let her go, because he can't live with himself if he changes her for the worse. With that, it seems that Delena may, in fact, have just broken up.

Katherine and Stefan are also in the midst of romantic turmoil. Katherine tells Stefan she wants his forgiveness. Stefan says that they just got swept up in the moment -- but that he is sorry that she is dying. Katherine gives Nadia a call and tells her that she will do the traveler spell. She believes that, deep down, Stefan knows that there is a chance for Katherine to be redeemed. But as Katherine talks to her daughter, she grabs her chest -- that's right, Katherine Pierce is having a full-on heart attack.

When we return from the mid-season hiatus, we'll find Katherine fighting for her life post-heart attack with the people who aren't super thrilled with her presence in the first place (namely, the long list of people that she screwed over in her 500-plus year long life). Will this be the end of the once-unkillable Katherine Pierce? And will we see a Delena reunion come the second half of this season?

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