Last Laugh — Franklin W. Dixon

From the back cover: "Attack of the flame fiend! A SAn Diego comic book convention turns into a real blast when guest speaker Barry Johns, a legendary publisher of Zenith Comics is kidnapped. But the Hardys can hardly believe their eyes. Johns is abducted by two characters straight off the illustrated page--the Human Dreadnought and Flame Fiend! Frank and Joe's investigation leads them into a confrontation with a rogues' gallery of comic book villains come to life, each armed with sinister, super-sophisticated powers. But the boys are determined to have the last laugh by unmasking the criminal mastermind behind the crazy comic book caper."