The title "Son of M" focuses on Pietro Maximoff following the events of "House of M". After attempting to commit suicide, a dying Pietro is brought to Attilan by Crystal. While Gorgon protests, Medusa grants Pietro asylum in Attilan until he is fully recovered. Once healed, a depowered Pietro tries to convince Black Bolt and Medusa to allow him access to the Terrigen Mists, but Medusa firmly states that Terrigenesis is a process forbidden to outsiders and that such a process upon a human could result in drastic mutations. Pietro manages to expose himself to the Mists regardless, and receives new powers before collecting both the Terrigen Crystals and his daughter, Luna, and returning to Earth. The crystals eventually end up in the possession of a black-ops sector of the United States government. The sector's subsequent refusal to return the crystals sparks a declaration of war between the Inhumans and the United States.