Passage

With little knowledge, no training and a host of unanswered questions, Richard and Karen go searching the galaxy for her parents’ birth planet, with the indispensable aid of her tutor. On the way, they discover why her parents had come to Earth and why no one had sought them since they failed to return home. They take a crash-course is interstellar navigation and piloting, and find out how well they have absorbed this new knowledge – being tested against an enemy that they never knew existed, in both ship-to-ship and hand-to-hand combat. Deserted and desert planets hone their teamwork, resolve and determination, posing problems beyond their combined abilities and leading them to radical, revolutionary choices.

After the abducted ones mobilise the immobile to cross hundreds of millions of miles of unforgiving vacuum, back on Earth the investigators are confronted by something suspiciously like a flying railcar, falling to Earth, apparently from space, and the frightening message declared by its occupants – a call to arms; to defend the planet from an impending invasion.