It sounds like a joke, or at least the kind of problem the X-Men certainly don't need to trouble themselves with: alligators in the sewers, the ultimate urban myth. But rumor becomes deadly reality when strange, reptilian creatures are found to be living under Manhattan. Huge masses of dead bodies are discovered in the creatures' lair, along with an ally in the fight: the Amazing Spider-Man! Reptilian creatures point to an old Spidey foe: Dr. Curt Connors, the biologist tragically transformed into the Lizard. But there's a larger, darker presence pulling the strings. As more people are transformed - including three of the X-Men - Spider-Man and the remaining mutants will have to battle foes on multiple fronts to survive the day and win their teammates back!