Basically, Harvey traps you in a room where the floor can flip like a coin. he stands on top of a pedestal and shoots at you while his henchmen attack. When he's out of ammo, he'll pull a switch causing the floor to flip over completely (sacrificing his henchmen, obviously), before he reloads. To avoid the flipping, you have to grapple up to a nearby gargoyle, then hit Harvey with a Batarang before he starts shooting again, to knock him off his perch. Once on the floor, beat on him as much as you can before he pushes you off and gets back on his pedestal.
Repeat a few more times to beat him.
REAL Campers Camp with a Purpose. REAL Campers Camp for the Team.