Fellow scientist and friend Bruce Banner comes to Reed looking for help. But his dark secret is soon revealed - he's the Incredible Hulk! When Banner reverts to his giant green alter-ego and goes on a rampage across New York City, the Fantastic Four must stop him.

Upon returning from a mission, the team finds their neighbors in the Baxter Building much more friendly than usual, but it soon becomes clear their "neighbors" are shape-shifting aliens - the Skrulls!

Things take a turn for the worse when Johnny gives his friend Frankie an unauthorized tour of Reed's lab. When Frankie is sucked into another dimension, Johnny goes in after her to prevent anyone from finding out. But as he does so, a small bug comes through the dimensional portal. Susan, Ben, and Reed now have to deal with the bug, while Frankie and Johnny are trapped in the other dimension.