Young Queen Elizabeth II is finding her way in postwar Europe, trying to repair friendships with foreign governments. Advised by her father's old courtiers, the Queen suspects that they may not have her best interests at heart. One of them is trying to sabotage her public appearances: that much she is sure of. When two bodies turn up in Chelsea, the Queen finds herself unwillingly used as the alibi for somebody very close to her. With the reputation of the monarchy at stake, Elizabeth knows she can't face these challenges alone. She needs support from someone she can trust. Therefore, she enlists the help of an ex-code breaker, Joan McGraw, to uncover the truth. But as Elizabeth and Joan are uncovering secrets from the past, the clock is ticking and they are in more danger than they know.

Queen Elizabeth II is looking forward to a traditional Christmas gathering with her family in Sandringham when a shocking discovery interrupts holiday plans. A severed hand has been found --- but even more unsettling, she recognizes the signet ring still attached to a finger. It belongs to a scion of the St Cyr family, her old friends from nearby Ladybridge Hall. As reporters speculate about the proximity of the crime to the Crown and the police fail to investigate a suspicious accident on her doorstep, Elizabeth quietly begins to mull over the mystery herself. Someone in the quiet county of Norfolk seems to have a secret worth killing for, and the Queen is determined to find out who and what that is --- even if that means discovering that someone in her close circle is a murderer.

At Buckingham Palace, the autumn of 2016 presages uncertain times. The Queen must deal with the fallout from the Brexit referendum, a new female prime minister, and a tumultuous election in the United States --- yet these prove to be the least of her worries when a staff member is found dead beside the palace swimming pool. Is it truly the result of a tragic accident, as the police think, or is something more sinister going on? Meanwhile, her assistant private secretary, Rozie Oshodi, is on the trail of a favorite painting that once hung outside the Queen’s bedroom and appears to have been misappropriated by the Royal Navy. And a series of disturbing anonymous letters have begun circulating in the palace.

It is the early spring of 2016, and Queen Elizabeth is at Windsor Castle in advance of her 90th birthday celebrations. But the preparations are interrupted when a guest is found dead in one of the Castle bedrooms. The scene suggests the young Russian pianist strangled himself, but a badly tied knot leads MI5 to suspect foul play was involved. The Queen leaves the investigation to the professionals --- until their suspicions point them in the wrong direction. Unhappy at the mishandling of the case and concerned for her staff’s morale, the monarch decides to discreetly take matters into her own hands. The resolute Elizabeth will use her keen eye, quick mind and steady nerve to bring a murderer to justice.