When a giant-sized bat ransacks Gotham harbor, Batman suspects that Dr. Kirk Langstrom is up to his old tricks, taking the Man-Bat formula again. Batman isn't the only one. Kirk's wife, Francine, is so distrustful of her husband that she decides to leave him. After further investigation, Batman discovers that this Man-Bat is not Kirk, but someone else, and thus he shames Francine's father into permanently destroying the formula.