Her Majesty, Queen Camilla, is aboard the Royal Train heading to a charity event in Sussex when disaster strikes – the train is derailed.

A tragic accident or a planned attack?

When, minutes later, a trusted aide is shot dead by a sniper, the police have their answer.

Despite all the evidence, Roy Grace is not convinced The Queen was the intended target. But he finds himself alone in his suspicions.

Fighting against the scepticism of his colleagues and the Palace itself, Grace pursues his own investigation. But when there is a second murder, the stakes rise even higher, and Grace is at risk of being embroiled in a very public catastrophe – and in mortal danger.

Failure at this level is not an option. But time is running out before a killer in the Palace will strike again . . .