Travelling over the Bavarian Alps in the Fantasticar to investigate reports of mysterious beings in the mountains, the Fantastic Four come under attack from Gorgon, an Inhuman. Their ship is forced down and they come into contact with the rest of the Inhumans, led by Medusa. She tells them that their hidden valley is known as the Great Refuge, and they have used their powers to keep it hidden from humanity for many years. She informs the Four that the Inhumans intend to reveal themselves to the human world and then rule it. The Four are imprisoned and Medusa uses a hypnotic ray on Ben, getting him to serve her. The rest of the team escape their cell, and Ben is ordered to capture Herbie. After Ben tracks Herbie down, the robot gets Ben to hit his head on the floor, restoring his memory. Reed and Sue retrieve the Fantasticar, and after avoiding attacks from a missile, Gorgon and Karnak, meet up with Herbie and Ben. However Crystal, another Inhuman, uses her power over the elements to ground the Fantasticar. Seemingly trapped by the Inhumans, the Fantastic Four have to find a way to stop the Inhumans' plans of conquest and free themselves.