Irish mob boss Erin McKillen has been taken into GCPD custody, but oddly enough, she wants to use her phone call to contact Bruce Wayne, and not her lawyer, but she may get another visitor sooner, as acid starts to drip through the ceiling, and the cops soon find half of the bat signal drenched in coercive acid.
Two-Face was trying to get Batman's attention, and he did. Bruce finds Harvey on a nearby roof, where he tells him that Erin has been caught and to believe in the values he once held as a DA. But this is Two-Face, and he doesn't believe in that sort of stuff anymore, so Bruce tires to take him in, but soon finds that Harvey has tied up a bunch of people with a bomb, which Bruce can't ignore. Once that situation is taken care of, of course, Harvey is nowhere to be found.
Flashback to years ago, Erin is being broken out after posing to be a dead body, but Batman gives chase, though is shaken off by a shotgun blast to the chest. Instead of leaving Gotham, Erin has one more stop to make, and that's to Harvey Dent's office, where he is with his wife. Apparently Erin's twin sister Shannon has died, and she believes Harvey is to blame. Claiming Harvey ripped her other half away from her, she feels it fitting to do the same to him, stabbing Gilda in the chest, and knocking Harvey out.
Back to the present, turns out Erin and Bruce were apparently friends when they were in school together as children. Erin tells Bruce that they both know the GCPD can't keep Two-Face away from her, and requests Batman's help, due to the Batman Inc. connections, a request that goes denied. When he leaves, Bruce asks Gordon what's next for Erin, and finds out she'll be held in Blackgate.
Things don't go well for Erin in Blackgate, as some men were hired/blackmailed to take care of her, prison style, and a big old fight breaks out. The fight comes to a momentary standstill when Matches Malone shows up, in defense of Erin. So, the mob turns on him, but since Batman is probably who put the thugs in Blackgate in the first place, They're no match for Matches either.
In the chaos, Matches manages to grab Erin, and escape the prisoners and guards, while using some C4 to blow a hole in the wall. But before the duo escapes completely, Matches injects Erin with a syringe to knock her out, and the next thing she knows, she's waking up in Wayne Manor, with Bruce standing over her.