Clayface has escaped, and while Gordon is in Arkham, learning about how Clayface's biggest fan and only audience had recently died, the giant mud pile is telling Penguin he's done paying off his debt, and abducting a new audience of his own.
Playing up the audience angle, Bruce believes Clayface might have gone to a location connected to his past, and has his computer cross-reference any location that ever played one of his movies, or a casting agency Clayface may have been in. To search all these locations, Batman calls in some help, but not the usual since, well, I guess everyone is still post Death of the Family mad, so Black Canary and Condor (boooooo!) it is.
While Batman and some of the Birds of Prey are out looking for him, Clayface has all his new "fans" tied up and restrained, with IVs placed in their arms. What's going in the IVs? Well, turns out, six months ago, while Joker was in town, Clayface got a strain of Joker venom from him, that won't kill, but it'll produce laughs. So as Clayface starts his act, the crowd laughs and cheers, against their will.
It doesn't take long for Batman to eventually find Clayface, and the two fight, which ultimately ends up with Clayface falling into a big... vat of something, that's heated, which keeps him from holding a form. With that, Gordon and Arkham find a new way to contain Clayface, and that's over an open flame.