Fantastic Four, Vol. 1

The Skrulls manage to send a power beam strong enough to penetrate rock all the way to Earth, feeing the Super Skrull from his underground imprisonment. He soon visits Dr. Franklin Storm in prison, and replaces the man. While the real Franklin Storm is held on the Skrull homeworld, Kl'rt breaks out of prison in his form. The FF initially lose him the first time they try to capture him, as Johnny and Sue don't want to see their father seriously hurt. The second confrontation is at the World's Fair. By this time, Reed has deduced the true identity of "Dr. Storm," and arranges a prisoner exchange with the Skrulls. The send Dr. Storm back to Earth with a booby trap designed to kill the four, but Dr. Storm takes the brunt of the blast instead, saving the lives of the FF at the expense of his own.