Charles Xavier and Erik Lensher have been in the midst of a battle for the future of mutantkind for decades. In that time, Xavier has founded a safe haven for young mutants and even trained a team, to covertly do good in the world. The X-Men and Erik's Brotherhood of Mutants have fought each other as often as they have worked together. Once again, this battle takes place, when a man known only by the name of Mr. Sinister has been capturing and experimenting on mutants.