Batman vs. Two-Face

Batman and Robin meet Gotham District Attorney Harvey Dent at a top-secret demonstration hosted by Professor Hugo Strange. With his assistant Dr. Harleen Quinzel, Strange operates a machine called the "Evil Extractor" designed to siphon evil from criminals and store it in a vat. Batman scoffs, noting there is no easy path to righteousness, but the machine does work—too well, as the Joker and other volunteers laugh manically in an attempt to overload the machine. The containment vat explodes, drenching Dent with liquified evil, which scars half his face and changes his personality.