The story is set in a future where humanity has colonized other planets. The protagonist is an astronaut who lands on a distant planet and discovers an ancient civilization that has long been extinct. As the protagonist explores the ruins of this civilization, they come across a mysterious creature lurking in the attic of an ancient building.The "thing in the attic" turns out to be an intelligent alien being that has been hiding for centuries, observing humanity's activities. It is revealed that this creature has been manipulating events on the planet for its own purposes, and it has the power to influence human minds.