The brown goo gives "Hagen" an instant face transplant and he can either go back to being a handsome movie star or be anyone he wants. In this episode, he uses it one time to fake being Bruce Wayne during a crime. Wayne, of course, is innocent, but accused and he/Batman have to prove their innocence.
The problem with the goo, by the way, like a lot of quick fixes, is that it doesn't last and it's addicting, so -Hagan/Clayface keeps going back to the place where the stuff is hidden: in lab belonging to bad guy "Roland Daggett," the guy who wants to take over Wayne Enterprises. It's like a drug, and Hagen has to have it.
Included in this episode is a thug called Bell whom Batman calls a "scumwad." That's a good name; never heard that one before.
Wayne is arrested and put in jail, ending this first part of a two-part episode.