"Death of a Hero!"
Dr. Franklin Storm is replaced by a super being in jail as he fools everyone, including Sue and Johnny that he is their father. The creature fights the Fantastic Four, but has all the same powers and Reed figures it out and exposes the creature as the Super Skrull.
Reed trades the Super Skrull for the real Franklin Storm, but he is booby trapped. The skrulls do not count on Franklin Storm finding his courage and taking the brunt of the trap and losing his life to save the FF.