Alden Walker-sport pilot and skydiver-finds himself and his light airplane mysteriously transported into an alien world: a parallel Earth peopled by exotic-looking humans as well as a host of animals that have evolved into human-like form, with human-like powers of thought, but which have retained their appetites for flesh and blood. Especially human flesh and blood. Accompanied by a beautiful indigenous woman with a score of her own to settle, Walker must set out upon a covert mission to retrieve a vital element from the creatures who have stolen it, employing his piloting and parachuting skills in combination with her superb swordsmanship. On their quest they will encounter a host of anthropomorphic predators, until they finally reach their goal: a mountain fortress occupied by a coldly calculating race of humanoid vampire bats. And upon the success or failure of their mission hangs the fate of both their worlds.