The Thing attacks an oil platform off the Texas shore. The Invisible Girl steals a valuable gem from a jewellery store. The Human Torch melts a statue when a town unveils it. Mister Fantastic shuts down a power plant. These impostors meet afterwards and reveal how they used their shape-shifting abilities and alien technology to perpetrate their misdeeds. They are Skrulls, and they plan on invading Earth. Fearing the Fantastic Four will stand in their way, these four agents want to ruin their reputation. The real Fantastic Four, in "an isolated hunting lodge," hear the news with dismay.

Part 2: Prisoner of the Skrulls
The United States Army surrounds the lodge. Wanted for the Skrulls' crimes, the Fantastic Four surrender. They escape from cells specifically designed to hold them and hole up in one of their "many secret apartment hideouts", in order to clear their names. They set a trap for the Skrulls by sending Johnny to sabotage a rocket launch, hoping it will draw them out. He melts through an unused gantry, avoids the army's artillery, and flames off behind a hangar. "Reed" and "Susan" pick him up and take him back to their hideout. A Fantasti-Flare out the window brings the rest of the team.

(Part 3) The Fantastic Four Fight Back!
A fight ensues and the Skrulls are taken prisoner. The Fantastic Four steal the Skrulls' rocket ship and find their mother-ship in Earth orbit. Posing as the Skrull agents, they trick the captain into believing that Earth is too dangerous to invade by passing off images from Journey into Mystery and Strange Tales as real. Reed volunteers to stay behind and remove any trace of the Skrulls' presence on Earth. Convinced his army would be slaughtered, the captain calls off the invasion and awards Reed a medal for bravery. On the way home the Fantastic Four pass through the cosmic rays again, causing the Thing to briefly return to human form.

(Part 4) The Fantastic Four ... Captured!
Once back on Earth the Fantastic Four clear their names by proving the existence of Skrulls to the military. The remaining three Skrulls transform into cows, and then Reed hypnotizes them into believing they are real cows. They are left in a field where they can live out their lives.

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