The X-Men, led by Cyclops, travel via Blackbird to Japan. During their search for Hisako, they discover that she is not the first Mutant to have gone missing. As they move ahead with their investigation, they also learn that the local people are extremely prejudiced against Mutants. Their investigation is hampered by the U-Men, a fanatical group of scientists who experiment on unwilling mutants. The X-Men invade the U-Men's hideout and what they discover is truly horrifying.