The group changed their name to "Mutant Force" and offered their services to the Mandrill and battled Defenders for him in his scheme to take over the U.S. Peeper became the field leader of the team, his powers allowing him to see his enemy's movements and plan for them. They battled Valkyrie, Wasp, Hellcat, Nighthawk, and Yellowjacket. Despite being successful at first in defeating the Defenders and capturing the female Defenders so that the Mandrill could enslave them, the group was defeated by the Defenders during their third encounter. Mutant Force was arrested, but they bargained with the U.S. government and became their agents in exchange for their presidential pardon. Their tenure as government agents was short. They battled the Hulk, and later testified before a secret tribunal against the Defenders. Peeper and Mutant Force were later employed by Professor Power's Secret Empire. Alongside Mutant Force and Mad Dog, he battled the Defenders once again.