While Reed conducts an experiment designed to cure Ben Grimm, there's an energy disruption which causes the experiment to go haywire! Now the Fantastic Four's powers have switched, but they don't have time to get used to them before they have to save the city. Because the energy disruption that caused the accident was the work of Doctor Doom, and now the FF, new powers and all, have to stop Doom before he destroys the city with his scheme.