In the midst of Zero Year, James Gordon has been betrayed by a dirty cop, and Roman Sionis is demanding he be thrown off a bridge, to make it look like a suicide. Gordon is well aware of how many people jump off this bridge and die, and knows no one walks away from it... until he does.
Flashback, following in the footsteps of the Red Hood gang, more masked criminals have flooded Gotham, and now the Black Mask gang are stealing these super batteries, which are projected to be like diamonds when an oncoming storm hits Gotham. With no help from his dirty partner Francis Laney, Gordon has done some digging of his own, and found that all the robberies have taken place within the vicinity of property owned by Janus Cosmetics, which is owned by Roman Sionis. He presents this info to Commissioner Loeb, but Loeb only wants Gordon working the vigilante case.
Of course Gordon doesn't listen to Loeb, and goes to talk to Roman in his office building, but doesn't get past the secretary. Nevertheless, Gordon takes a notice to Roman's mask collection, and the fact he's got police officers moonlighting as private security, which means they're on the take. Gordon then presents this new info to Loeb, who eventually decides to assign an IA officer, Zachary Henshaw, to Gordon, to further investigate his theories.
This officer is the guy who sets Gordon up to be taken down by Sionis, but he never expected Gordon would survive the bridge ordeal. Gordon walks back into Gotham, but is suspicious as to why Henshaw would go along with it, gathering so much evidence on his fellow crooked cops. So on a hunch, Gordon breaks into Henshaw's apartment and finds all the evidence.
Returning to the GCPD, Gordon finds Henshaw already spinning a tale that Gordon seemed depressed lately, all but pointing his finger to him jumping off a bridge. Henshaw is met with a punch to the face and Gordon telling him he's arrested. Laney puts a gun to his head, and Loeb comes in. Gordon then brings out the folder he got from Henshaw, with all the dirt on the crooked cops that he may need if any of them fall out of favor with Sionis, and there's plenty on Laney too. With Laney's finger ready to pull the trigger, the butt of a gun hits the back of his head, as a young Harvey Bullock saved the situation from getting any worse.
When all is said and done, Sionis has already gone into hiding, he's become the Black Mask, and cops like Henshaw and Laney start showing up dead. With everything going to shit in the GCPD, Gordon revisits the scene where he almost died, and it's revealed that Batman caught him falling off the bridge.
Then a back-up set in present day with Man-Bat, and a bunch of tiny little bats eating up people, like we saw last issue, I think?