Sub-Mariner is in the Pacific Ocean (where he's been in Lemuria for the past 2 issues) when he meets sea creatures fleeing from an area containing 2 active volcanic islands, and dead creatures closer in. When he reaches 1 of the islands he's attacked by the Human Torch. He assumes that Johnny Storm is angry about his recent fight with Thing (#8). He battles through the firestorm and uses 1 of his wristlets as knuckledusters to avoid his fist touching the flaming body. But he doesn't manage to knock HT into the sea and so his foe is able to drain all the moisture from him, leaving him too weak to fight.
But then the Torch reveals that he's not the member of the Fantastic Four but the WWII android Human Torch in his red costume. Namor's old ally now contacts his boss the Mad Thinker via a communicator on a golden collar. Thinker orders him to kill Subby but Torch can't bring himself to slay his old friend. Thinker gets very angry and makes the collar inflict pain (and for some reason HT daren't remove it). But all this allows Sub-Mariner to crawl to the water, and once immersed he emerges refreshed for battle.
Thinker is also in contact with his old and current ally Puppet Master (we just saw them with Egghead in Avengers #63) who scorns him for not being able to control the Torch. And reminds him that he himself was able to control Sub-Mariner with his radioactive puppets. This riles Thinker and in his rage he accidentally smashes the microphone that enables him to give HT commands.
Even without those commands Torch is still ready to fight Namor. But SM swims rapidly in circles to create a whirling mass of water that sucks HT in and drags him out to sea. He then jams the disoriented Torch between 2 half-submerged rocks and demands to know why he serves the Thinker.
Torch explains how Thinker reactivated him but he had no memory. So MT told him of his history (with supporting evidence like probably newspaper clippings and several film clips). He was the 1st android, created by Prof Horton in 1939, called the Human Torch (as seen in Timely's Marvel Comics #1). Film clips show him years later with his youthful flaming partner Toro, which does stir HT's memory. Then Thinker gives a biased recount of Fantastic Four Annual #4 claiming that the FF tried to destroy him there. But everything agreed that he was an android built to serve a master. And his master now was Thinker ...
... who gave him the job of carrying a device into the nearest volcano and using his flame to cause an eruption which would power up the device. MT didn't tell him why, but later he overheard his master conferring with Egghead and Puppet Master and learned that they planned to rule America and then the world. Now Prince Namor is understandably angry about that because the world includes Atlantis. But Torch tells him that their fight has broken his control collar so he's a free 'man' once more and will help fight the villains.
Meanwhile the 3 villains hold a remote meeting by closed-circuit TV and decide to test run their plan. The Thinker's Pacific base and that of Puppet Master in the Caribbean combine with Egghead's orbiting space station to inscribe an energy-absorbing arc across the middle of the US, shutting down all power. Egghead then broadcasts a message to America threatening to blackout the whole country. He will contact them in an hour to announce his terms for not doing that.
But now HT and SM force their way in to Thinker's lair under a dormant volcano on another island. Thinker's defences strike back but our heroes are undeterred. Then the foe fires a ray gun which starts to make the Torch grow uncontrollably hotter. Subby starts to destroy a machine which Thinker is guarding, deducing correctly that it will halt the villains' plan. But he keeps firing his ray at Torch who finds he can't now turn off his flame. Namor smashes the ray gun but it's too late. Torch is now yellow-hot and his attempts to further wreck the machinery risk causing a catastrophic explosion. So Sub-Mariner rips off a sheet of asbestos-lined metal and uses it to carry Torch out of the volcano and into the ocean.
The water douses HT's flame (and revives SM again). And Torch sees in the reflective metal that it has washed blonde dye out of his hair leaving it brown. And his memory returns to him letting him realise he's *not* the Human Torch. Instead he's Toro and he now recalls that after HT disappeared in 1955 (ie his comics appearances stopped) he grew up and got married. But then he read about Torch's recent revival and death (FF Annual #4) and went to his 'funeral' where Thinker met him and drugged him. He now realises that the villain brainwashed him.
The duo see Thinker escaping in an airship. Toro flames on and flies into the rocket's exhaust, propelling it to crash onto the island destroying the lab and killing them both.
Chars listening to Egghead's broadcast include Black Panther, Vision, Wasp, Yellowjacket, Iron Man, Nick Fury and Dum-Dum Dugan, all of whom are involved in this overall plotline.