Mimi was later contacted by the criminal Baron Helmut Zemo to join his version of the Masters of Evil. Her first assignment was to help bust the female Yellowjacket out of prison, but Mimi was captured in the subsequent battle with the Wasp, Black Knight, and Paladin. She was bound and gagged and arrested. Later, she formed a romantic and criminal partnership with the similarly-empowered Angar the Screamer, at one point battling the Avengers Hawkeye and Mockingbird. The pair impersonated Hawkeye and Mockingbird, but battled them and were defeated. Mimi was also seen among the various female superhumans aboard Superia's cruiseship, where she battled Captain America and Paladin. Angar was eventually mortally wounded by a gunshot during a robbery attempt that went sour, and died in Mimi's arms after they escaped. Mad with grief, Mimi screamed, burning out her power. Immediately afterward, she was contacted by Baron Zemo once more, and she accepted his offer to join a formative Masters of Evil. Zemo allowed Mimi to be nursed back to health, and his accomplice, the Fixer, gave her new powers via a voice-augmenting harness and high-tech implants in her neck based on technology from the villain Klaw. With her newly transformed powers, she resumed the use of her given name Melissa, and adopted the identity of Songbird as a member of the Thunderbolts, a new Masters of Evil group posing as superheroes to win the world's trust while secretly plotting world conquest under Zemo's direction. However, Melissa and most of the other Thunderbolts grew to like their heroic roles. In particular, Melissa began to truly grow into her own and even began a romance with her teammate Abner Jenkins, alias MACH-1, formerly the Beetle. Ultimately, the Thunderbolts turned against Zemo, foiling his attempt at world domination and rescuing the Avengers in the process. Melissa continued to serve with the team, who operated as a team of outlaw superheroes.