Sundered from Earth during the time of the Black Death, frightened and bewildered humans are transported by benign aliens to a planet of a nearby star. Slowly they recover and a much changed society flourishes; science is re-learnt and discoveries are made. A scientist, Sir Giles Fitzgerald, desperate to know more of the origins of his people, sends a message to Earth but, in so doing, unwittingly alerts the attention of forces inimical to humankind. It's up to an ill assorted group of adventurers to find their original saviours else the fate of both worlds is dire...