On Krakoa, all mutants are now welcome, including those whose behavior poses a threat to the new nation. To give them a place while keeping them under control, Mister Sinister assembles a particularly unstable team: Havok, Psylocke, Empath, Wild Child, Nanny, Orphan-Maker, and John Greycrow. These Hellions are sent on missions that other mutant teams would rather avoid, but their personalities and traumas make every operation unpredictable. Between violent confrontations, internal tensions, and Sinister’s manipulations, the group must learn to function together even though some of its members can barely tolerate one another.