Doctor Will Magnus is flooded with mail requests to rebuild Platinum. Consumed with loneliness, Platinum had constructed a robot duplicate of Magnus. In turn, the Magnus robot constructed it's own Metal Man, Plutonium, and set it to detonate. To save the world, Platinum wound herself around "Magnus" and Plutonium, binding them together. Next she wound herself around their mobile jet platform, then bound it to a departing rocket. Plutonium detonates on the Moon, destroying itself, Platinum and "Magnus". In order to reconstruct Platinum, Magnus would need to journey to the Moon, to recover vital elements of her makeup. Deeming the task too difficult, Magnus decides to build a brand new Platinum. Correcting for the earlier "flaw" in the responsometer that gave the original Platinum human emotions, Magnus builds the new Platinum as a perfect robot.
The Metal Men greet the new Platinum with warm affection, only to be rebuffed by it's cold, emotionless derision. Believing that Magnus' Metal Men are faulty in their construction, Platinum suggests that Magnus take it out on a trial run. In this way, Platinum can more strongly demonstrate the proper operational parameters for machines. Mercury boils hot in the face of Platinum's assumed superiority. Tin, however, fears that Platinum will convince Magnus to scrap the Metal Men. Magnus departs with Platinum in the Metal Men's jet platform. Upon boarding the craft, Platinum nearly crushes Magnus' foot when she steps upon it. Magnus attempts to impress Platinum with the beautiful spectacle of a magnificent sunset. The Platinum robot is unmoved. A sudden updraft pitches Magnus off the jet platform.
Platinum makes no move to rescue Magnus, until he specifically orders it to catch him. Platinum catches Magnus, after he has already plummeted beneath the surface of the river. Once caught, Platinum merely holds Magnus, instead of pulling him to the surface. Magnus is on the verge of drowning, when he sees Mercury and Iron descending towards him. Mercury brings Magnus back up to the jet platform, where they find Platinum violently resisting the efforts of the other Metal Men to force it to let go of Magnus. Barely conscious, Magnus orders Platinum to release him. Platinum complies. Returning to their headquarters, Magnus orders Platinum to leap into his industrial metal smelter. Magnus, with the Metal Men, journey to the Moon, to recover the necessary elements to rebuild the original Platinum.
Back on Earth, Magnus completes the reconstruction work. A revived Platinum immediately resumes her amorous attentions towards Magnus. When Platinum continues to disrupt Magnus' work on a space catapult craft, Magnus suggests Platinum cook them a meal. Platinum begins to fry some eggs. Suddenly, the eggs violently erupt from the pan, growing to enormous size. Magnus comes to Platinum's rescue, then surmises that the "egg" is really an amoeba. The micro-organism was probably picked up when they brought Platinum's elements back from the Moon. As soon as it was brought to Earth, it awakened from it's dormancy, and attacked. The amoeba, continuing to grow, breaks through the kitchen door. Lead becomes a giant barrier between the amoeba and the the Metal Men, but the amoeba eventually topples Lead.
As the team runs from the amoeba, Tin laments that he is too weak to be of any use to the Metal Men. Iron attacks the amoeba, only to have the creature separate into multiple amoebas, which overwhelm Iron. Mercury forms a final barrier against the amoeba, buying Magnus, and the remaining Metal Men, time to reach the jet platform. As Mercury falls, Magnus attacks the amoeba with the weapons on board the jet platform. The jet platform's weapons array merely transforms the amoeba into a mutated herd of micro-organisms. Tin transforms himself into an enormous tin cup, which Gold then forces the micro-organisms to enter. Platinum then binds Tin to Magnus' space catapult. Magnus takes Tin into orbit, then launches him into a cosmic ray storm, in the hopes that the radiation will destroy the micro-organisms. Platinum is forced to release Tin. As Magnus returns to Earth, Platinum chastises him for so coldly abandoning Tin.