A century ago, Charles Darwin's revolutionary theory of evolution rocked the civilized world, and the outraged Anglican church went on the warpath against it. In a mansion in London's affluent Brunswick Gardens, the battle is intense, as that most respected clergyman, the Reverend Ramsay Parmenter, is boldly challenged by his beautiful assistant, Unity Bellwood - a "new woman" whose feminism and aggressive Darwinism he finds appalling.
When Unity, three months pregnant, tumbles down the Parmenter's staircase to her death, Thomas Pitt, commander of the Bow Street police station, is virtually certain that one of the three deeply devout men in the house committed murder. Could it have been the Reverend Parmenter, his handsome curate, or his Roman Catholic son?