As the third installment of the X-Men series opens, the world has entered a relatively peaceful period for mutants. There's a mutant-tolerant president of the United States, a blue furry mutant named Beast (Kelsey Grammer) heading up the Department of Mutant Affairs, and Magneto's shape-shifting femme fatale, Mystique, has been captured. The tranquility is shattered when Worthington Laboratories, using a powerful mutant boy, develops a serum that eliminates the "mutant X gene" permanently.