The story unfolds from the discovery, by Kenyon, of an anonymous 19th century diary, in which appear the figures of four friends similar to Kenyon, Miriam, Hilda and Donatello. The uncanny resemblances make the friends seem doomed to relive a mystery which took place a hundred years previously. During a visit to the catacombs, Miriam encounters a mysterious, pale, ghostlike figure wearing a black cape, to whom they refer thereafter as "the Persecutor", and who appears to exercise an inexplicable hold on Miriam.