This issue picks up where the last one left off. Johnny Storm (AKA The Human Torch), following an argument with the Thing, and generally feeling under-appreciated by the team, quits and flies off. The rest of the Fantastic Four go in search of him. Fearing he is a threat, the military and police are hunting him as well.
When the Thing finds Johnny and wrecks his hot rod, he flees to the Bowery to hide. There, in a flophouse, he discovers the Sub-Mariner!
The Sub-Mariner is disheveled and suffering from amnesia, but Johnny helps restore his memory by dropping him into the sea. The Sub-Mariner swims off, only to find his home city of Atlantis destroyed by nuclear bomb tests; he swears vengeance upon mankind.
Using the Horn of Proteus, Sub-Mariner summons Giganto, a massive sea monster. The Fantastic Four, once again reunited, defeat the monster by having the Thing carry an atomic bomb into it's stomach.
Sub-Mariner then plans to summon more sea monsters with the Horn of Proteus, but Invisible Girl steals it. When Sub-Mariner grabs her, she becomes visible. 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.