He discovers that the Yithians on Earth died out eons ago (their civilization destroyed by a rival, utterly alien pre-human race described as "half-polypous" creatures) but the Yithian minds will inhabit new bodies on Earth after humanity is long gone. His tenuously held sanity is challenged when he discovers the proof he seeks—and that not only do remains of the Yithians' past civilization still exist on Earth; but also still remaining are those who destroyed them. It is also mentioned that the current appearance of the Yithians is not the original; but one acquired during a previous mass-projection of the minds of their race when disaster beckoned, leaving the original inhabitants to die in the bodies of the Yithians.