The following contains spoilers for DC vs. Vampires #7, now on sale from DC Comics.

DC vs. Vampires #7 reveals that Batgirl is on a mission to slay Nightwing -- and only Harley Quinn can help her infiltrate Gotham City.

The issue, which outlines the aftermath of the DC Universe after descending into a vampire-run dystopia, shows Batgirl and the remaining resistance heroes hiding out in the remains of Kandor. There, they plot out ways to defeat Dick Grayson, who violently slaughtered Batman and most of the other members of the Bat-Family in DC vs. Vampires #6.

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After listening to her friends squabble over their next move in the battle against the undead, a vengeful Barbara Gordon says, "None of this matters as long as their king is around. The war continues and we continue to lose it until he falls. I'm going to Gotham to kill Dick Grayson."

Unfortunately, Gotham City has become a tightly-guarded vampire haven, making any infiltration mission a difficult affair. According to Constantine, Harley Quinn managed to make it outside of Gotham City after it fell to the undead, and could share this knowledge with Batgirl. Unfortunately, she's a prisoner of Hugo Strange, who appears to be working alongside Professor Pyg, the Thinker and Frankenstein to harvest her spinal fluid. The final page of the issue shows Harley imprisoned but threatening to smash each of her captors' brains with a hammer if she ever makes it free.

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Harley Quinn previously appeared in DC vs. Vampires #6 as a member of the Suicide Squad and fought alongside Deadshot to subdue King Shark and Parasite, two of her Task Force X companions-turned-vampires. After telling Amanda Waller that she was up against bloodsuckers, Waller activated the bombs embedded in King Shark and Parasite's brains. Captain Boomerang also received an explosive lobotomy, thanks to Harley failing to inform her boss that her Australian boomerang-chucking comrade was not, in fact, undead.

The DC vs. Vampires: Killers one-shot further elaborated upon Harley's story, showing her as the ruler of Gotham's underworld in the aftermath of the vampire apocalypse. After she was given a vial of Lex Luthor's blood -- which contains an anti-vampirism formula -- by James Gordon, Harley injected it into herself and became a reluctant hero. Hugo Strange's current desire to study her spinal fluid is likely related to the injection.

DC vs. Vampires #7 comes from writers James Tynion IV and Matthew Rosenberg, artist Otto Schmidt, letterer Tom Napolitano, cover artist Guillem March and variant cover artists Leirix and Francesco Mattina. The issue is on sale now from DC Comics.

Source: DC