After having a "Julie Madison just turned into my dead mother" dream, Bruce wakes up in an unfamiliar apartment, being watched over by a kid named Duke Thomas, aka the kid we saw Bruce rescue in the first issue of Zero Year. Things have gotten bad while Bruce has been out, like post-apoctaliptic bad, and time for Gotham has been set on a new scale by it's ruler The Riddler, welcome to Zero Year (THEY SAID IT!)
The City is in ruins, but some still work to save it, like Jim Gordon, who is out and about, up to something. Bruce calls to Alfred on their special linked phone, and gets all the details. Riddler's taken the city hostage, bombs everywhere, all tech under his control, weather balloons of deadly toxin looming in the sky, the city is truly his... but free for the taking to anyone. The Riddler comes on screen every night and urges Gotham to be better, become smarter, and will give the city back to anyone who can stump him with a riddle, thus Duke's rock solid attention towards crossword puzzles, believing he can find something to help save Gotham.
*Note: I've done five of these posts already, I'm going to just burn through the rest of this*
So, after Bruce leaves Duke's apartment and heads back to his old Brownstone base, some Government special ops guys parachute into the city and meet up with Gordon. Meanwhile someone tries to challenge Riddler, but him being the Riddler, he knows the guy's answer before he even finishes the question, and it was a riddle the dude made up himself.
Riddler then brings attention to the Government ops agents in the city, them having not gone unnoticed, and puts them through a physical test after he doesn't accept their $50 million payoff. He starts a chain reaction of buildings crashing their way, and surrounds them by motion detector gun turret robots, but there's a way out... If Gordon shoots one, they could all go down, but the question is which one, and of course there's wordplay in it. One of the Government guys is all "shoot that one" but Batman shows up in the shadows and tells Gordon to shoot the camera robot because I don't know, read the explanation for yourself, and what do you know, it works... But there's still the buildings coming down towards them. Batman gives them a way out, and with that, Gordon and Batman finally start to work together, for Gotham.