After responding to a break-in at the chemical labs at Stagg Industries, Batman rescues a security guard named Rex Mason who had been exposed to a weaponized toxic gas known as "Project Metamorpho." Soon, Rex begins to mutate and gains the ability to manipulate the elements of his own body. Terrified and unable to control his new abilities, Rex becomes a fugitive. Realizing that this metamorphosis is slowly killing Rex, Batman sets out to find a cure. But Rex is only concerned about one thing: Sapphire Stagg (the woman he loves) and he would risk all of Gotham to be with her. But her father Simon Stagg holds secrets of his own and will do anything to keep them apart.