Dr. Matthew Thorne, losing his medical license and forced into becoming the crime doctor by his younger brother, crime boss Rupert Thorne, must perform delicate surgery on Rupert. He can't do it alone, and kidnaps Dr. Leslie Thompkins to assist. Batman discovers Leslie's disappearance, and rushes to track her down - and has an additional interest in Matthew, because he was a medical school classmate of Bruce Wayne's father Thomas.

En route to an upstate prison, Killer Croc escapes and leads Batman on a dangerous chase through the wilderness. After throwing Batman temporarily off his trail, the reptile-man takes refuge with a group of retired circus freaks, and convinces them to help him. When Batman arrives, Croc and the freaks band together to capture him.