John waits a day, and goes where he's told and delivers his message.

"The Joker wants to arrange a meeting with Mr. Moriarty. He says it's time to put aside our differences."

And they have to have been expecting it, because the person he talks to doesn't even ask for proof of the message's origin, just nods and says she'll see about contacting the boss.

It's two more days of back-and-forth before they get their meeting - not with Moriarty, but with his local representative, or something. Everyone is very vague on the details, for which he can't really blame them, all things considered. Somewhat to John's surprise, Moriarty's people accept the Joker's offer of one of his many abandoned warehouse lairs (seriously, does the man have a collection?) as a meeting spot. They show up early. John feels... out of place. The Joker is meeting with a mob boss to discuss an alliance against the guy who just took over the city, and for some reason John Blake is invited.

He still hasn't told Gordon a thing. It's not that he's afraid to, exactly, more that he can't even figure out how to bring it up. How do you explain that the Joker is actually weirdly approachable as long as you can make your peace with his sense of humour? Not to mention the little girl with the wings. Definitely don't mention the little girl with the wings. If he mentions the little girl with the wings, Gordon will probably be out the door before he can even try to explain.