Batman: The Ultimate Evil is a novel written by Andrew Vachss and published in 1995 by the Warner Aspect imprint of Warner Books. Vachss was an attorney specializing in child abuse cases, as well as a crime novelist best known for his series of books featuring the character Burke, a private investigator who also takes on child abuse cases.
A representative from DC Comics approached Vachss about the possibility of writing a novel featuring Batman. Viewing this as an opportunity to reach a completely different audience, Vachss agreed and wrote a draft. He continued with his themes concerning child sexual abuse and explored the topic of child sex tourism. The publisher required Vachss to follow certain rules, like making a clear distinction between fiction and reality and prohibiting the Batman character from killing, cursing, or having sex.
In the story, billionaire Bruce Wayne, who as a child witnessed the murder of his parents Thomas and Martha, encounters the social worker Debra Kane, who takes Wayne to check up on her clients: he sees clear cases of child abuse and brave but futile resistance to it. Wayne's loyal butler, Alfred Pennyworth, gives him the secret files from his mother's investigation into a pedophile ring, which had led to her and her husband's murder, illuminating the darkest mystery of Wayne's childhood.
As Batman, Wayne reopens his mother's investigation and, through a series of informants, is led to a child sex tourism syndicate using the southeast-Asian country of Udon Khai. Batman travels to Udon Khai and, with the help of a local rebel force of guerrilla fighters, topples the kingpin who controls the industry. In the process, he avenges the murder of his parents. The book ends with a non-fiction essay, by journalist David Hechler, entitled "Child Sex Tourism".