Like Aquaman in The Enemy Below, Metamorphosis chooses to focus on a guest hero and his story, leaving the Justice League to play more of a supporting role. Rex Mason, aka Metamorpho, takes the spotlight in Metamorphosis, and delivers a solid episode about one of the more classic DC heroes.

Simon Stagg is developing a new mutagen that promises to turn normal humans into superbeings. His henchman, Java, accidentally spills the mutagen on a train and causes it to crash. Green Lantern manages to save the day, and meets up with an old war buddy of his, Rex Mason, who also happens to be on the train. Mason also works for Stagg but has no knowledge of the new mutagen.

Rex takes Lantern to his home, and introduces him to his fianc? Sapphire Stagg. Batman tells Green Lantern about the mutagen, and John accuses Rex of importing the illegal substance. Rex can?t believe John would accuse him, and asks him to leave.

Rex confronts Stagg about the mutagen, but Stagg refuses to answer any of Rex?s questions. Rex decides it?s time to leave Stagg Enterprises, and announces to Stagg that he?s leaving and taking Sapphire Stagg with him.

Simon Stagg arranges for Rex to ?accidentally? be caught in a security leak and infects him with the mutagen. Rex is transformed into a monster and escapes from the hospital. Green Lantern promises Sapphire that he?ll bring Rex back, but Simon convinces Rex that it was John who was jealous of Sapphire and arranged for Rex?s accident. At the end of the episode, Rex beats Green Lantern and is about to kill him.