The Sub-Mariner has returned! Calling upon his mighty sea creature army, he will have his revenge on the human race. It's up to the Fantastic Four to stop him.
Picking up where the last issue ends Johnny Storm following an argument with the Thing, and generally feeling under-appreciated by the team, quits the Fantastic Four and flies off. Soon after the other members of the Fantastic Four go in search of him and fearing him to be a threat the military and police set out in hunt of him as well. The Thing finds Johnny working on his hot rod and the two fight before Johnny flees to the Bowery to hide. In a Bowery flophouse the Human Torch then discovers the Sub-Mariner.
The Sub-Mariner disheveled and suffering from amnesia has his memory restored when Johnny Storm realises it is him and drops him into the sea in an attempt to restore his memory. The Sub-Mariner swims off to his home only to find his home city of Atlantis destroyed by nuclear bomb tests and he swears vengeance upon mankind. Using the Horn of Proteus, the Sub-Mariner summons Giganto, a massive sea monster and the Fantastic Four, once again reunited, defeat the monster by having the Thing carry an atomic bomb into it's stomach.
Sub-Mariner about to attempt to summon more sea monsters with the Horn of Proteus, is unable to do so when the Invisible Girl steals it from him. As the Sub-Mariner grabs her she becomes visible and the Sub-Mariner instantly falls in love with her and promises to give up his war on humanity if she will be his queen. Sue agrees, but when the other team members try to intervene, he vows to have both Sue and his war!
Note: This is the first issue to feature the rephrased tagline "The world's greatest comic magazine!" which has appeared on every issue since.