Responding to a break-in at Stagg Industries, Batman rescues a security guard named Rex Mason who had been exposed to a weaponized toxic gas called Project Metamorpho. Soon, Rex begins to mutate, with the ability to control the elements in 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 the woman he loves – Sapphire Stagg – and he’d 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.