Left behind by a long-vanished civilisation, the mysterious portals offer a means of transport many times faster than warp travel — as Captain James T. Kirk and the crew of the USS Enterprise have inadvertently discovered.
Having defeated the hostile computer program which guards an abandoned Kalandan outpost, Kirk and his crew are exploring the artifical planetoid in the hope of discovering more about the ancient apparatus which has hurled the Starship Enterprise a distance of a thousand light years. But the reactivated Gateway has attracted the attention — and the avarice — of various alien explorers, not least a mysterious race who claim to be none other than the enigmatic Kalandans themselves!