Complete summary (with spoilers)
In a huge vessel in the space of the Microverse, his owner, Psycho-Man, the Micronauts and thee of the Fantastic Four watch a amazing scene. The Human torch, having joined the Microverse thanks to the Prometheus Pitt, has keep his original height. So, it's like a gigantic flame being he appears to the others ones.
Quickly, all of them feel weak. The giant flame of Johnny Storm had consumed all the oxygen of the Psycho-Man construction and one by one, the heroes fall unconscious. Commander Rann, using a little air supply in his helmet has enough time to tell to the Human Torch to turn off his power. But the Fantastic Four lost his consciousness even so and fall heavily on the constructions around him. Arcturus remain conscious but Psycho-Man knock down the little Micronaut with a back of his hand. Finally, Biotron, last of the Psycho-Man opponents is destroyed by huge magnets came out from the ground.
Some time after, all the heroes regain consciousness. Expect Johnny Storm who is bind by numerous little robot, the others heroes are prisoners in little tubes of glass, the machinery of Psycho-Man aspiring their energy and feeding the giant. Thanks to the combined strength of Acroyear and The Thing, the little men and women succeed to evade. They attack their giant enemy and his minions expect Bug who, protected by the power of Invisible woman, enter in the huge psycho-manipulator. The insectoid Micronaut uses his rocket-lance to sever a cable of the machine. Instantaneously, Psycho-Man lost his energy and is forced to transfer his brain in a more little armor.
The battle continue hardly. A Reptos, minions of Psycho-Man try to slain Bug, leaving the psycho-manipulator. Jasmine intercept their natural enemy but she is taking away by the flying lizard. Marionette follows a robot who picking up the rubbishes of the battle and found Biotron and Microtron totally repaired by the robots of Psycho-Man. The three Micronauts join the others heroes who are flying from the army of the owner of the space. Unfortunately, Jasmine had been murdered by the Reptos and Arcturus has to snatched his corpse from the hands of Psycho-Man.
Despite their sadness, all the heroes join their respective spacecrafts. The Human Torch and his companions come back to Earth while the Micronauts fly far from the vessel of their enemy.
The first adventure of their new journey has a expensive price: the death of a Micronaut.