Not many days start with a marble and end on the other side of the universe, but for the twins Kass and Tycho it is just that kind of day. Hidden under a pyramid-shaped mountain in the forest, they find a mysterious spacecraft, and before they know it, they are hurled farther out into space than any other human being has been before them. How are they going to find their way back home? Are they really alone onboard the spacecraft? And what really hides in the Forbidden Solar Systems? The quest to return to earth sends the twins on a journey out into an expansive alien universe where they must defy dangers, enemies, warlike aliens, cosmic rays and exploding stars. But the greatest danger is something they can’t even see …