Damon has been hiding some pretty big skeletons in his closet, and in Season 5, Episode 9 (“The Cell”), they all came pouring out.

Now that The Vampire Diaries has ditched the doppelganger drama, we’re finally seeing some much-needed character development from our favorite vamps. Damon has always been a dark and broody figure in Mystic Falls, but “The Cell” shed some light on the snarky vampire.

For five years Damon was Dr. Whitmore’s lab rat. Upon his return to Mystic Falls in 1953, he was poisoned with vervain and taken by the psycho doc. There, he is physically tortured and experimented on by Dr. Whitmore, whose disgusting brand of “research” includes cutting out parts of Damon’s eyes and other vital organs. His goal was to study how vampires cure themselves — and how their blood can cure others. [And this is where I started to actually feel bad for Damon.]

But Damon wasn’t alone. His only confidante was another one of Whitmore’s test subjects, Enzo, a European vamps captured from the frontlines during World World II and taken to Whitmore. Enzo’s friendship was the only thing that kept Damon alive in that cell.

Eventually, the two conspired to escape Whitmore’s dungeon. It seems that they were taken out of their cells once a year to attend a Whitmore Christmas party, where the crazy doc would parade his experiments around and demonstrate how their blood has healing properties. Enzo decides that if one of them were to sacrifice his blood rations to the other for an entire year, that vampire would be strong enough to kill everyone at next year’s Christmas party. So after a crushing game of rock, paper, scissors, Enzo gives his ration of blood to Damon for one year, and at the Whitmore Christmas party in 1958, he’s strong enough to escape.

In true Damon Salvatore style, he kills Dr. Whitmore and every Augustine member at the party — he even sets Whitmore House ablaze. But sadly, he’s unable to break Enzo out of the vervain-laced cage. Instead of trying to set his friend free, he flips his humanity switch and leaves him there to burn. This would explain why Damon was such a d-bag when we met him back in Season 1. He couldn’t deal with the fact he killed his best friend, so he got rid of all emotion, and he didn’t want to make Stefan feel sorry for him, so he never told his brother — or anyone — about his past as an Augustine vampire. [Funny how it took FIVE SEASONS to get to this story… take that Caroline!]

But that wasn’t all Damon was hiding. It turns out Damon and Elena’s summer of love wasn’t all playful picnics and steamy hookups — somewhere in between the butterfly kisses and the “I love yous,” Damon went on Whitmore family killing sprees. Five years of physical and mental torture at Whitmore College pushed Damon over the edge, and he swore that he would get his revenge on the Whitmore family by killing everyone in the family’s bloodline — except for one, so he could carry on the name, and Damon could kill the next generation of Whitmores.

Now, this wouldn’t seem like the biggest deal (vampires kill humans, amirite?) if Aaron wasn’t a Whitmore! That’s right: Aaron’s full name is Aaron Whitmore — oh, daaaaamn — and Damon is the one who killed his parents. Now imagine poor Aaron’s shock after realizing Damon is the reason you don’t have any family left — we probably would have shot him in the head too, Aaron.

Elena, on the other hand, doesn’t know what to think. Aaron unknowingly led her into a trap, and she was also taken by Dr. Wes. But after Damon dropped a few truth bombs on her, she’s more confused than ever. Damon was still killing Whitmores when they were together, which means he was lying to her. Come on, Damon! This is Relationships 101. However, Elena doesn’t have time to process the news because by the time Aaron shoots him in the head, she’s taken by Dr. Wes and strapped to his lab table… next to ENZO!

While I wasn’t surprised to see Enzo alive, I was shocked to see how deranged he had become. I guess over 70 years of torture can turn even the toughest vampire a little cuckoo. Clearly, Enzo was the one who killed Meghan. I’m intrigued to see how his inevitable reunion with Damon goes — will he remember his former friend, or will he want to rip his heart out?

But Damon wasn’t the only Salvatore dealing with his issues this week. In an effort to forget about his own emotional scars, Stefan encourages Katherine to enter her feelings into a diary. Katherine, being Katherine, isn’t one for writing down her feels. She’d rather call you an idiot and call it a day. She also sees what kind of game Stefan is playing, so she calls in reinforcements: Caroline Forbes!

I had hoped there would be more interaction between Stefan and Caroline, but it looks like the writers had another ship in mind. In the end, it was Katherine’s plan that broke Stefan out of his funk. It turns out Stefan was suppressing his heartbreak over Delena and deflecting it on his PTSD and Silas. Wow. As if we didn’t see that one coming.

After a seriously awkward moment between Stefan, Katherine, and Caroline — in which Care Bear nearly catches the two making out in the safe — Stefan and Katherine meet up in the library… where there kiss. Stefan and Katherine kiss. It happens. And it’s pretty great. Honestly, I never thought I’d be shipping Katherine and Stefan, but these two are the most compelling characters on The Vampire Diaries, so of course I ship it!

$#*! Vampires Say

“What kind of sentimental idiot writes down everything they feel?” — Oh, Katherine, if you only knew.

“I’m your sober sponsor, and I heard that you needed help.” — Caroline Forbes to the rescue!

“Don’t worry. I sanitized it.” — Of course you did, Caroline.

“You know, most people would buy me dinner first.” — It’s nice to see Damon hasn’t lost his humor, even when being tortured.

“You’re a vampire, she’s a human… the relationship would have been doomed from the beginning.” — How times have changed, Damon.

“Since 1958? I’ve lost count.” — Typical Damon.

Catch the next episode of The Vampire Diaries on Thursday, December 5 at 8 p.m. ET on the CW, followed by an all-new episode of Reign.

Crystal Bell is an editor at Wetpaint Entertainment and our resident fangirl for all things The Vampire Diaries. Follow her on Twitter and Google+!