Extraterrestrial intelligences are operating on Earth undetected by the public. Life-Int-Ltd, the world's largest security service, becomes aware of this. Sigurd Westall, a new employee of the company, is set on the aliens immediately after his basic training. No one, apart from his direct superior, knows that he has had a special ability since puberty. He is assigned to a team of specialists who set out on the trail of the aliens. When it comes to a direct confrontation, it is only thanks to this ability that he survives. Together with the female spaceship Paurusheya, Sigurd Westall reaches Saturn's moon Japetus. There he finds a huge lunar station embedded in the ridge at the edge of the dark hemisphere. The station is also the destination of the strangers in the small spaceship he is chasing. Sigurd initially tries to find his two kidnapped colleagues on his own. But when he is quickly discovered by the aliens, he is forced to fight back. He receives help from a source that causes him to plunge into a personal crisis as the story progresses.