The X-Men—mutant protectors of a world that fears and hates them. The Avengers—Earth's mightiest heroes, the greatest super-team ever assembled. When the Scarlet Witch of the Avengers and Rogue of the X-Men all disappear under mysterious circumstances, each team's search leads them to more questions than answers. When the X-Men appear to attack a high-security government installation, the Avengers must track down the mutants and learn the truth behind the abductions before it's too late.