The Infant Terrible was a member of an unknown alien race who landed on Earth and, with no knowledge of what the planet or its inhabitants were, unleashed its massive powers on anyone or anything that approached it. The infant was first seen creating a giant maze out of the New York streets, sending a massive toy top loose on the city, and creating multiplying robots that marched blindly down the streets. But the Fantastic Four appeared and stopped its playthings by directing the police and authorities to set off every car horn, fire engine siren, and air-raid siren in the city to distract it. Then the infant sat down to eat an ice cream soda which it created out of a blank wall until a group of reporters and photographers startled it, forcing it to place them on an opposite building with its mind. At the same time, the Invisible Girl snuck up to get a closer look, and when she turned visible the infant became scared and pulled a meteor storm towards Earth, which the Fantastic Four narrowly escaped.
Later, the gangster Big Joe kidnapped the infant by enticing it with candy, then tried to force it to steal an armored car for him and enlarge a small diamond to an enormous size. But the infant only wanted to have fun, and soon turned the money from the truck and the diamond into pigs, mud, and a hatching bird. Big Joe got upset, but the Fantastic Four, minus Mister Fantastic, showed up and stopped the gang, imprisoning Big Joe in a set of tires for the police to pick him up. The infant ran during the struggle and when confronted it sent a rock monster after the three team members. The Human Torch and the Thing quickly took care of the monster, but the infant panicked again and encased the three in a pliable, fireproof bubble and traveled back to New York in the blink of an eye.
Back in the center of the city, the infant felt trapped and accosted by everyone around it, and so it unleashed an angry tantrum that sent bolts of energy down among the crowded New Yorkers. Being ignorant of Earth weaponry, the infant lifted every purse, hat, and parcel from the onlookers into the air. In the panic, Alicia Masters was nearly trampled and later passed out. But during his tantrum, Mister Fantastic had an idea to send a signal out into space, and his gambit succeeded as the infant’s alien parents traveled to the planet Earth to claim their offspring. They arrived just as the infant had caught sight of the Earth’s Sun and was prepared to do something potentially disastrous, but its parents stopped it and bid the Earth a final farewell as they took their errant child back to their home planet.