Larry Rambow is the son of Dr. Zolten Rambow, a scientist whose hatred of war set him to creating a device that would end war forever. His father created such a device that would conceivably neutralize any weapon on Earth, but when he was ready for the final test he asked his son to help him. Larry agreed, and donned a suit that would protect him from the energies of the machine. But when Zolten turned it on an oxygen leak set off the atomic energies and Larry was bathed in destructive energy. Instead of it killing him, it turned him into a being of living energy and he burned his way out of the lab and into the streets.
Larry, as the energy monster, wandered the streets attacking buildings and anyone who got near with his energy rays. When he passed by a clothing store where the Invisible Girl shopped, the energy he was giving off shook the building, and she saved the customers inside and left to investigate. She found Larry firing away and endangering everyone around him with his expanding energy. Dr. Rambow emerged moments later from his car, feigning ignorance of the origin of the monsters, but pleading for Susan to not harm it without first trying to speak to it. The Human Torch, mourning his separation from the Inhuman Crystal as she had flew from the city’s pollutants, flew out of the Baxter Building and nearly fell to his death when the energy being’s powers stifled his flame. When Larry was far enough away, Johnny flamed back on and attacked him, but the flames were absorbed by Larry’s energy.
In an attempt to stop him from doing further harm, Susan sealed Larry in one of her force fields and begged Johnny to fetch Mister Fantastic. He left and Larry fought against the unseen wall, until Susan’s own stamina was exhausted and she fainted. Larry instinctively attacked her, but Reed appeared in time to deflect the ray with his own body. Reed was prepared to stop Larry at any cost, but Larry’s father tried to reason with Reed, which made Reed suspicious and he dragged out the true story from him. Reed, knowing Dr. Rambow, asked if he had a failsafe device back at his lab, and when Rambow agreed, Johnny carried him there to get it.
Reed used his stretching powers to encircle Larry in a giant, rubber ball, maneuvering him towards the local Armory. He left enough of a hole for Larry to fire a blast that tore open the door, and they rolled inside. Reed released Larry, exhausted, but Larry’s father returned with the device. Reed set it to the proper calibrations before fainting, and Dr. Rambow took the responsibility upon himself and fired the device at Larry. The machine worked and Larry returned to normal, feeling as if he had awoken from a dream. Larry’s father fainted, as well, and Larry thanked a recovered Reed, recognizing that he was all that his father had said he was. Before he could say much more, the Fantastic Four rushed away to see to their teammate, the Thing, who lay frozen in Reed’s contraption meant to return his humanity to him.