In 1920s London, “Lady Detective” Maud West enlists newly published Agatha Christie to covertly investigate a dangerous mystery, propelling the unlikely duo through mounting threats and blackmail in a quest to deliver justice.

In early 1920s London, Maud West has gained a public reputation as “London’s Lady Detective,” though the title is largely of her own making. Her self-written newspaper accounts bring her notoriety, but not the professional respect she craves. Instead of high-profile investigations, she is routinely assigned divorce work, missing persons, and blackmail—cases that rarely challenge her talents or elevate her status. When a frightened woman comes to her office claiming she is being stalked by a strange man, Maud senses a rare opportunity to prove her skill. As she digs deeper, she discovers that her client’s troubles are tied to a clandestine gang operating within the city. The threats quickly escalate, and soon Maud herself becomes a target.

Elsewhere in London, Agatha Christie is both a new mother and a rising author, thrilled to see her first detective novel in print. Yet she hungers to observe a real investigation firsthand. Maud West’s exploits in the newspapers captivate her imagination and fuel her desire to study genuine detective work.

To Agatha’s astonishment, she receives a message from Maud requesting a private meeting. Maud outlines the increasingly perilous case and proposes a partnership: As a public figure tied to the investigation, she needs someone inconspicuous and sharp-minded to assist her. Agatha, a crime novelist rather than a known detective, is the perfect covert ally. Together, the celebrated detective and the rising mystery writer become entangled in a dangerous, twisting web that will test their ingenuity, courage, and trust as they work to bring justice to light.