The Turing Protocol: A Novel

“An incredible debut thriller where the past can be changed to save the future.” —Don Winslow, #1 internationally bestselling author

A riveting speculative historical suspense debut told in alternating timelines that asks: Will the most powerful invention in history save the world—or destroy it?

In the midst of World War Two, Enigma codebreaker Alan Turing finds himself on the brink of a discovery that will change the world: a way to send a message back into the recent past. But when his invention successfully averts disaster on D-Day, the danger it poses in the wrong hands becomes terrifyingly clear. As Turing’s enemies close in, only one decision is possible: Nautilus must be kept hidden from the world, safe in the care of the only person he can trust.

Seventy-five years later, Annabelle McIntosh’s life is upended when she learns she will become the latest custodian of the greatest secret of the modern age—Turing’s Nautilus machine. Following in her family’s footsteps, and bound by Turing’s strict principles governing the use of his creation, Annabelle is soon faced with the same impossible choices.

Weaving together past and present, The Turing Protocol honors Alan Turing—a genius who was misunderstood and persecuted by his own time—and takes the reader through pivotal moments in history, including the Cuban Missile Crisis, the dissolution of the Soviet Union, and 9/11. All of this leads us to the present day, where Annabelle must prevent major catastrophe—but when the stakes are at their highest, is using Nautilus the perfect solution? Or a risk too dangerous to take?

© 2025 HarperAudio (Audiobook): 9780063485105

Release date

Audiobook: 2 December 2025