Classic Andre Norton tale:
Was he an android? Or was he, as he thought, the rightful Emperor of Inyanga, imprisoned on an alien planet and kept in mind lock while an android imposter ruled in his stead?
Even after he met his double, he could not be sure, but he knew his life was worth nothing if he fell into the hands of his rival.
Hiding from pursuit in a remote (and supposedly haunted) corner of the great palace, he was summoned to a strange fire by the sound of an ancient harp, and then was drawn into a world that mirrored his own--but a world so beleaguered by enemies from within and without that it seemeed it must perish.
Yet, somehow, he had to save it, and with it, the whole of Inyangan civilization.