Like virtually all of the superheroes from Earth-2149, the Fantastic Four succumbed to the interstellar virus known as the Hunger Gospel. Transformed into the living dead, the team no longer cared about protecting the world as they had done before, becoming focused solely on hunting down the living to consume their flesh. Still possessing his incredible intellect unlike the zombies of cinema, Dr. Reed Richards - Mr. Fantastic - knew that the Earth would soon be devoid of life at the rate the undead plague was spreading and began researching into means of travelling to other dimensions to find more food and spread the infection.
Richards soon completed a teleporter device and discovered a new parallel Earth suitable to invade: Earth-1610 (the Ultimate Marvel universe). Reed established a line of communication with his counterpart from Earth-1610, creating a holographic projection of himself as he was before his infection. He convinced the other Reed to visit his world and gave him the technical information to build a teleporter device of his own. Of course, when Reed-1610 arrived in Earth-2149, it became obvious that he had been tricked.
The zombified Fantastic Four - or the Frightful Four as they would later be named - greeted Reed-1610 and told him what had happened to their world and the reasons behind their deception. At that point, they pursued the younger Reed through the sewers, intent on devouring him and then invading his Earth after. Reed is able to escape and the Frightful Four break off their pursuit, heading back to the Baxter Building to use the teleporter and invade Earth-1610.
The Frightful Four encounter their Fantastic Four counterparts who manage to seal them inside a nuclear containment area. With the zombies contained, the Ultimate FF try to find a way to save their Reed, but he is fortunately saved by Earth-2149's version of Erik Lensherr, aka Magneto. With the teleporter on Earth-2149 destroyed and the Frightful Four trapped on Earth-1610, no other zombies from the ruined Earth can follow and have no way of building another teleporter.
The zombified FF are kept in confinement which they see as merely temporary accommodations since Ultimate Reed refuses to kill them. Zombie Reed informs his healthy counterpart that they fully intend to escape when the time is right and spread the zombie virus across the planet. A week after their confinement, the Frightful Four enact their escape plan, fooling the guards into believing that the zombies have a working teleporter device made from a pen and hair. Of course that is impossible, but Reed Richards is well-known for his uncanny intellect and outlandish inventions. In reality, the zombie Sue Richards has turned them all invisible with her powers, but the guards nonetheless open the doors to investigate. The zombies then kill the guards and break out, killing and eating dozens of people on their way to the Baxter Building's lab where they intend to build a new teleporter.
In order to stop their undead counterparts, the Ultimate FF seek help from their arch-enemy, Victor van Damme (Doctor Doom). Doom assists the FF and singlehandedly defeats each of the zombies. Using his magic, he extinguishes Inhuman Torch's flames, snaps off Thing's arm, necrotises Sue completely and conjures a swarm of maggots to eat Reed. Doom then used the completed teleporter to dump the Frightful Four's remains back on to the street of their native New York.
- The team name "Frightful Four" was first used in the mainstream Marvel universe (Earth-616). This group of villains were not zombies, however, or any other kind of monsters. The team has consisted of various super-powered humans and also robot and alien members.