The machine is real. Alan Turing built it, and it can send a message eight weeks into the past. Eight weeks: enough time to stop a disaster. Save lives. Change history.

It has never been a weapon and it has never been for sale. From the beginning, Nautilus has operated under protocols as strict as anything Turing ever devised. Only a descendant may use it. Only to avert catastrophe. Only ever backwards, and only ever eight weeks. For three generations that guardianship has held, passed down in secret and protected by a family who understood exactly what they were holding.

Annabelle is the current guardian. She is also a British cabinet minister on a steep rise, which makes her a woman with secrets and very little room to move. When a message arrives at the receiving station in a London vault, she already knows what it means: her older self, eight weeks ahead, has seen something bad enough to reach back for.

Her husband is spying on her.

Edward has spent a career in his wife's shadow, wheeled out for the cameras and ignored the rest of the time. Edward is a man who has always felt owed. And he has worked out something nobody in the family could guard against. A machine that can reach into the past does not have to be used to save the world. It can be used to make money.

The money comes fast but so does the exposure. A business partner asks the wrong question. A murder follows that is recorded as an accident. And in Moscow, a service that has been watching Edward, recognises a chance to strike at the heart of British government. 

From a Dorset farmhouse to a Boston lecture hall, from the terraces of Monte Carlo to a boarding school on Lake Geneva, the circle of people who know about Nautilus widens past anyone's ability to protect them. An American physicist is drawn in. So is a child. And the protocols that governed the machine for eighty years turn out to be exactly what protocols always are: an agreement between people, worth precisely what those people are worth.

Nautilus is the sequel to The Turing Protocol, and it moves fast, doubling back on itself in eight-week jumps as the consequences of each message land. 

It is a thriller about money, marriage, betrayal and the machinery of statecraft, built on a question that has stopped being hypothetical: not whether we can build something powerful enough to rewrite the world, but whether anyone can be trusted to hold it once we have.