In this the riveting sequel to The Beekeeper's Apprentice, Mary Russell has metamorphosed from able apprentice to skilled detective in her own right. After a tedious visit from relatives, Mary is looking for respite in London when she comes across a friend from Oxford. The young woman introduces Mary to the enigmatic Margery Childe, leader of the New Temple of God, a charismatic sect involved in the post-World War One suffrage movement, with a feminist slant on Christianity. Intrigued and curious, Mary begins to wonder if the New Temple is a front for something more sinister. When a series of murders claims members of the movement's wealthy young female volunteers, Mary, with Holmes in the background, starts to investigate, but events spiral out of control as the situation becomes ever more desperate, and Mary's search plunges her into the worst danger she has yet faced...