When retired mining engineer Yarrow is disturbed after midnight by Barnabas Fosworth, he assumes that he is just a curious eccentric. But by helping Fosworth in his search for the mysterious girl he seeks, Yarrow soon finds his life inexplicably threatened by a mystical sect who believe that taking life is forgivable, since death is only a transition. Entombed in a cavern in the Mendips, Yarrow discovers the ancient secrets that have their origins in paleolithic paintings; and it is only through this new knowledge that he can hope to escape a very unpleasant death.