In a “parallel reality”, most of the X-Men have become zombies. It is this reality that Mr Fantastic has disappeared to. He forms an alliance with Magneto, one of the remaining mutants still alive. They travel through the subway in search of the Baxter Building. There, they can teleport to Mr Fantastic’s “home dimension”, away from the zombie invasion.
But their path is blocked by the masses of zombies, including the Avengers, X-Men, and countless other superheroes and supervillains.