Stephens had to solve the mystery of the centuries-old house that stood still -- or Earth would be destroyed! At first Allison Stephens knew only that there was something strange about the house and its sinister inhabitants. Then he stumbled onto the spaceship and learned of the catastrophe that threatened to obliterate the universe from the heavens -- a catastrophe that the masked immortals from The House that Stood Still could prevent. But the immortals planned instead to escape to another planet -- leaving Earth to its terrible fate. Only one of them, the unearthly beautiful Mistra Lannett, agreed to help save the world. During the fateful days that followed, Stephens and Mistra met the challenge to defeat the most indestructible aliens the world had ever known!