from the dustjacket of the 1970 Howard Baker edition:
This book is constructed around the exciting idea of the interweaving of three dimensions of time. The prehistoric world of 500,000 years ago when Pithecanthropus (Java Man), our first recognizable ancestor, roamed the swamps and forests of a tropical world; the world of Eoanthropus, a less distant ancestor who lived 200,000 years ago when primitive man's spirit of enquiry had enabled him to make some slow progress; and 1929, the modern 'civilised' world and, more especially, the world of the Heston menage. The Hestons are two beautiful young women, their father, a priest whose strict orthodoxy makes him more medieval than modern and their uncle, Lord Coomebridge, a kindly scientist whose dearest ambition it is to discover a perfect specimen of Java Man.
A group from each time play out the same drama, the enactment of which provides the basis of a novel which is at once original, ingenious and with its novel treatment of the supernatural, strangely disturbing.