While one billionaire playboy returns to Gotham, similarly, another returns to Seattle, but Oliver Queen is still playing dead when he secretly reveals himself to his old friend Emerson. The reunion is short lived as Oliver soon finds out that his mother, Moira, headed to Gotham to offer aid during Zero Year, and now will be stuck in the middle of the storm about to hit Gotham.
Moira Queen is at a shelter in the Narrows, with her security guard, John Diggle, suggesting now is the time to leave Gotham, an idea that Moira doesn't entertain. But the idea becomes a little bit more appetizing once the shelter is attacked by Killer Moth, who is after Moira and her money, thinking she'd be a pretty good person to ransom off.
On the outskirts of Gotham, Oliver manages to sneak in, still wanting to be unnoticed, and straps on his early Green Arrow gear, all while Diggle is trying to protect his mother from Killer Moth. Moth's weapons manage to push Diggle back with compressed air, allowing him to approach Moira, until an arrow goes through his hand. Green Arrow? HAH! No. BATMAN WITH A CROSSBOW, because why not?
Batman and Killer Moth start going at it, and soon Oliver shows up as Green Arrow too. The two have a nice back and forth, exchanging blows to Killer Moth. When all is said and done, Batman tries to escort Moira out of the chaos, but she declines, saying she's with the new vigilante. Batman basically goes "whatever" and takes Killer Moth away.
Oliver tries to hide his identity from his mother, but she's too smart, and recognizes her son, and while she's happy to see him, she knows he's different and asks what happened to him on the island.
Then there's a back up of Oliver coming to Diggle for help one month later, they become partners, then apparently Roy's introduction into the "team" is what eventually causes a rift between the two.