Celia's mother, Lily Taylor, has befriended a Hindu guru, Dr. Akananda, and it is he who discovers what's wrong with the young couple.

The book then moves back in time to the reign of Edward VI, as lovely young Celia de Bohun and her guardian aunt take up residence with the noble Catholic family of Anthony Browne as "poor relations."

She creates a scandal when she becomes infatuated with the family chaplain, Stephen Marsdon, who in turn desires Celia but does not want to break his vow of chastity.

Time passes; King Edward dies and his persecution of Catholics ends, only to be followed by his successor Queen Mary I's persecution of Protestants; the Browne family fortunes prosper under the Marian reign; and sympathetic characters harden into detestable ones.

The Manor House setting in Green Darkness at Ightham Mote was faithfully replicated at Cape Elizabeth, Maine by Charles Henry Robinson.