London, 1921: Mabel Canning is proud to be a modern woman working for the Useful Women’s Agency, carrying out tasks for gentlewomen from flower arranging to washing muddy dogs. But when she answers the door for wealthy widow Rosalind Despard, she almost chokes on her cucumber sandwich when she finds a soldier’s body on the doorstep. As she offers tea to the policemen of Scotland Yard, Mabel can’t resist getting drawn into the investigation.

Spring, 1918. The Great War is at a crucial stage, the Germans are making one last push into France, and the Allies are struggling to hold them back. Battle lines are shifting, and men, and their machines, are being sent up and down the front to shore up defenses. Major Heathcliff Lennox, and his batman Greggs, are told to report to their new HQ. They set off on a sunlit day to fly the distance, but the enemy is never far away, and disaster strikes. They're sent crashing to the ground behind enemy lines, where life, death, and love await.

We are 40 years into the future, and London is a city in decay. John Watson has returned from medical service in the war in Afghanistan and lives by himself in a run-down part of ​town. On his way home from work, he stumbles upon a beaten man in the street – unconscious and completely naked. His chances of survival are minimal. The same evening, a passenger plane crashes in Richmond Park. There are several hundred victims, and Watson and the mysterious man are left to their own devices.

December 1899. After the death of her beloved grandmother, Cleopatra Fox moves into the luxury hotel owned by her estranged uncle in the hopes of putting hardship and loneliness behind her. But the poisoning of a guest on Christmas eve throws her new life, and the hotel, into chaos. Cleo quickly realizes no one can be trusted, not Scotland Yard and especially not the hotel’s charming assistant manager.

June 1933. Independent, young Kitty Underhay has been left in charge of her family’s hotel, The Dolphin, on the tranquil English coast. But when several rooms are broken into and searched, including Kitty’s own, she quickly realizes that something out of the ordinary is afoot at the hotel. Soon, rumors are flying in the cozy town that someone is on the hunt for a stolen ruby. A ruby that Kitty’s mother may well have possessed when she herself went missing during the Great War.