Peggy McArthur and her husband Norman and their son lived a nondescript life in Queens, New York. That all changed one day when Norm went grocery shopping and stumbled into a battle between the Fantastic Four and their foes Tyros the Terrible and Doctor Doom. During the course of the battle, Tyros -- whose body was being consumed by the Power Cosmic -- turned on Doctor Doom, fusing his armor. When Tyros was crashing down to Earth after a battle with the Silver Surfer, he collided with Doom's body, seemingly slaying him.  However Doom used a body swapping technique he learned from the Ovoids to switch bodies with Norm. In stead, Norm was killed in Doom's body, while Doom lived on in the body of Norman McArthur. 
Unable to gain access to the Latverian embassy, Doom returned to the McArthur home where he forced Peggy to stay home as his prisoner, while he worked on a new Invincible Man suit to break into the embassy. At that time he managed to dupe the Fantastic Four into helping him and captured the group. Seeing her "Norman" breaking into the embassy, Peggy went with her neighbor Sarah to try and help him. Unaware that her husband's body was inhabited by Doctor Doom, she helped knock out the Invisible Woman as they battled.  Doom then used his magical expertise to summon the Beyonder to him in the hopes of forcing him to restore Doom to his former glory. Mister Fantastic suddenly realized that during the then-recent Secret Wars,  the version of Doctor Doom present was actually from the future where be Beyonder had restored Doom back to normal. Convincing the Beyonder to ensure this came to pass, Norm McArthur and Doctor Doom were both restored to normal. While McArthur was reunited with his family, Doom was sent back in time to fight in the Secret Wars.  The fate of Peggy and her husband following these events are unknown.