The mystery of May 10, 1994 continued in Season 6 episode 4 of “The Vampire Diaries.” With the addition of Kai (Chris Wood) to the mix, Bonnie (Kat Graham) and Damon (Ian Somerhalder) discovered that there was a way out of their “personal hell” – but it came with a horrifying twist.

Episode 4, “Black Hole Sun,” kicked off with Kai continuing to annoy Damon about why the eldest Salvatore believes that May 10, 1994 is his “very own personal hell.” Damon’s not interested in sharing his story, but Kai has a pretty solid argument – He knows how to get out of this alternate reality, Bonnie’s magic will help them leave … but Kai wants to know why Damon deserves to come along.

Turns out that the “worst thing Damon ever did” happened on May 10, 1994. Damon showed up at the Salvatore mansion in Mystic Falls about a month prior (right around the death of Kurt Cobain in April) to the date. He hadn’t seen Stefan (Paul Wesley) in 50 years, but he claimed to want to turn over a new leaf. Zack Salvatore (Chris William Martin), a distant relative, welcomed him in. But Damon had ulterior motives for returning to town – he wanted to continue to make Stefan’s life a living hell.

While Damon stayed at the Salvatore Mansion, he slowly began switching out the vervain in Zack and his pregnant girlfriend, Gail’s, coffee. It was when the verain was fully out of their system that he began feeding off them.

When Stefan made the discovery he snapped his brother’s neck and removed his daylight ring before he woke up. Needless to say, Damon was not happy with Stefan’s move. The second the sun went down, Damon went on a killing spree … ending with pregnant Gail.

Damon fled Mystic Falls, leaving Stefan to clean up his mess. Stefan was forced to compel Zack to forget about Gail and the baby, but he couldn’t hide all the other bodies. The high body count lead the town to form the Founder’s Council and Stefan had to flee town.

So, how did Damon’s story about May 10, 1994 relate to him, Bonnie and Kai escaping that alternate reality? The date is also a personal hell for Kai – because it’s the day he murdered all his siblings. Kai, who came from a family of witches, was sent to this world as punishment by his coven. And while he doesn’t have the ability to do magic, he does possess a contraption that when aligned with the eclipse will get them back to their world.

Unfortunately for Damon, Bonnie’s not interested in releasing Kai back into the world after the horrific crime he committed. And while she was appalled over learning about Damon’s involvement in murdering a pregnant woman, she let Damon know that he was different from Kai. While Kai didn’t feel any remorse for his crimes, Damon was continually punishing himself.

Bonnie promised Damon that they would find a way to ditch Kai and get back to their loved ones. But Kai dropped another bombshell – he can harvest Bonnie’s power, kill them both and leave this world … or they can agree to help him and they can all leave together.

Meanwhile in present day, everyone was doing their best to track Sarah (Gabrielle Walsh) in order to prevent her from spilling the beans about the vampires in town. However Elena (Nina Dobrev) put that mission on hold in order to check out Stefan’s “system” for moving on.

Since he still can’t return to Mystic Falls, Stefan wanted to return to his “life” in Savannah. But Elena truly couldn’t believe that Stefan could start over so easily like that – So Stefan broke down the process. Step 1: Move to a new place. Step 2: Make your own story. (For this scenario Stefan and Elena pretended to be a newly engaged couple with a baby on the way.) Step 3: Move on in 30 years when people start to realize that you’re not ageing.

Elena liked Stefan’s process and agreed to let him move on if he promised to keep in touch. However Stefan’s true process emerged the moment that Elena walked out of the bar they were hanging out in. A man at the bar began to fight him after claiming that Stefan was behind his brother’s hospitalization. But instead of fighting back, Stefan just allowed him to pummel him. The man only stopped when Elena swooped in and compelled him to leave.

Angry that Stefan lied to her, Elena berated him for letting the death of Damon affect him so much. But Stefan found it hard to listen to her – especially since she erased Damon from her mind. He told Elena all about Alaric compelling her, and Elena didn’t believe him until she spoke to Alaric. Confused as to why he would erase her memories of Damon, Elena understood everything when Alaric handed over a journal that Elena wrote for herself. 

“You’ve been given the chance to start over,” the journal entry read. “I want you to take it. I want you to be happy.”

Elena decided to follow her own advice and chose not to have Alaric return her memories to her. Elsewhere, another Mystic Falls resident admitted to having some memory issues – Tripp (Colin Ferguson). Matt (Zach Roerig) decided to infiltrate Tripp’s secret vampire killing organization, and the new Mystic Falls leader revealed that a vampire had compelled him to forget that his wife was killed right in front of him. The memory only returned when he crossed over the Mystic Falls border to check on his grandmother after the gas explosion at the Mystic Grill. Ever since then, Tripp has made it his mission to kill every vampire stalking the innocent people of Mystic Falls.

Episode 4 of “The Vampire Diaries” concluded with Sarah showing up at the Salvatore mansion to talk to Jeremy (Steven R. McQueen) about a photo she found while ransacking the place – the photo featured her mother with a man. Sarah explained that her mother, Gail, was dumped at the hospital when she was six months pregnant. She was dead on arrival, but the doctor’s managed to perform an emergency C-section and save the baby. Sarah spent three months in an incubator but survived. Jeremy revealed that Sarah’s dad was none other than Zack Salvatore.

Sarah’s father’s identity was a big reveal, but not the biggest jaw dropper of “Black Hole Sun.” Stefan’s girlfriend, Ivy, returned from the dead as a vampire.