The search involves the British practitioners of a religious cult called The Children of Lights with roots in Shanghai, China.

The plot picks up in the summer of 1924 near an ancient circle of standing stones on Orkney Island, shortly after religious fanatic Thomas Brothers, who seeks to unleash psychic energies through human sacrifice, shot Holmes's artist son, Damian Adler.

Holmes's search for medical help to save his son's life takes him to Holland, while Mary travels through Britain in an effort to keep Estelle safe from Brothers and his allies.

Brothers' shadowy connections have led to a conspiracy deeply entrenched in the highest echelons of government.

Mycroft Holmes finds himself questioned and under suspicion and the family members are actively pursued by Scotland Yard.