Bonnie's (Kat Graham) life remains in danger as Damon (Ian Somerhalder) and Enzo (Michael Malarkey) continue to find ways to cure her. But she will spend time learning the mystery behind the secret vault in The Armory in the next episode of "The Vampire Diaries" season 7.

The trailer for the episode, titled "Kill 'Em All," shows Virginia's (Aisha Duran) return, and she warns Bonnie that "Whatever's inside that vault, it wants out."

It was revealed in the previous episode that Bonnie's missing cousin, Lucy Bennett (Natashia Williams), was forced to seal the vault in The Armory while Virginia's sister, Yvette, remains inside. Virginia's other sister, Alex (Mouzam Makkar), believed that she had killed Lucy to make sure that no one could ever open the vault again. But Alex seems determined to do everything to free Yvette from the vault.

In the trailer, Yvette's voice can still be heard from the other side of the vault. But it seems like Bonnie will keep her promise to Virginia when Damon asked her what she just did. When Alex warned everyone to run, Bonnie just said: "No one's getting out."

Meanwhile, Stefan (Paul Wesley) also appears to be sticking to his promise of helping Damon and Enzo complete Rayna's (Leslie-Anne Huff) hit list to help cure Bonnie. In the trailer, Stefan is seen on the phone, asking the person on the other end of the line who the next person on his hit list is. Can he finish the task before Bonnie's time runs out?

The official synopsis for episode 20 states that "With Bonnie's life at stake and an uphill battle ahead of them, Damon and Enzo lead the charge to save Bonnie before her condition worsens. Stefan reluctantly teams up with Matt (Zach Roerig) for the sake of Bonnie and uncovers the truth behind Matt's anger towards him. Elsewhere, determined to help her best friend, Caroline (Candice King) joins Alaric (Matt Davis) on a mission and quickly realizes how much she's missed her former supernatural lifestyle. Finally, after their plan takes an unexpected turn, Damon makes a fateful decision that will forever change his relationship with Bonnie."

"The Vampire Diaries" season 7 episode 20 airs on Friday, April 29, on The CW.