Leonora Spencer has an acquaintance with death. Sixteen years ago, only she survived the brutal murder of her family. Now, as an assistant in her uncle's London morgue, she uses her photographic memory to catalogue details for his coroner reports. She also isn't opposed to helping him during postmortems if his skilled hands begin to shake. After a thief breaks into the morgue and steals a locket from a young woman's corpse, Leo is determined to understand why, even if it means going against Detective Inspector Jasper Reid's express orders to keep her nose out of it.

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.

May 1941. One of the senior choristers of St Paul's Cathedral choir, Dr Edwin Roberts, is found beaten to death in the crypt of the Cathedral. Coburg and Lampson are called in to investigate, and when they get there, Coburg is pleasantly surprised to be greeted there by Arthur Waterson, now sporting a dog collar, someone he was at Eton with many years before. Waterson believes that there may be a connection between the very precious books that are houses in the Crypt and Dr Roberts' work at Bletchley Park.

Following the death of her husband, Lady Darby has taken refuge at her sister's estate, finding solace in her passion for painting. But when one of the house guests is murdered, her brother-in-law asks her to aid the insufferable Sebastian Gage - a fellow guest with some experience as an inquiry agent. While Gage is clearly more competent than she first assumed, Kiera isn't about to let her guard down, as accusations and rumors swirl.

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.

Cherringham - a quiet town in the Cotswolds. Nothing ever happens there, or so it seems - until one morning a woman's body is found in the river. A terrible accident, according to the police. But is this true? Sarah believes there must be more to it. In Jack, a former NYPD homicide detective, she finds a partner who is willing to start investigating with her. They soon find out that things are not as clear as the police want them to be ... This first - of many cases brings Sarah and Jack together in an unlikely partnership.

December 1940. With the Luftwaffe pounding the city nightly, Londoners seek refuge in underground stations. Aldwych has been taken out of service to provide shelter for the British Museum's priceless Elgin Marbles, as well as civilians escaping the bombing. When the body of a young man is discovered on the tracks, wearing evening dress but barefoot, Detective Chief Inspector Coburg and Sergeant Lampson are on the case. Before long, more bodies are discovered, and Coburg's wife Rosa becomes a target for the brutal killer.

London, 1941: Miss Jane Treen is at her desk, strong black coffee in hand and fluffy ginger cat by her side, when her top-secret government work is interrupted by an urgent call to Devon. A woman has been found dead in a lake in a place where she shouldn’t have been. Jane needs to gather the clues and find the killer before someone else from the agency gets hurt… Shy and handsome code-breaker Arthur Cilento is bewildered by the arrival of the efficient Miss Treen and her cat Marmaduke.

Determined to find the men responsible for her disgraced father's murder, Lady Arianna Hadley disguises herself as a man and contrives to be hired as a chef in one of London's aristocratic households. But when the prince regent is poisoned by Arianna's special chocolate dessert, she finds her own quest has become intertwined with a far more deadly intrigue. The earl of Saybrook is asked by the government to investigate. When someone tries to kill them both, they become reluctant allies in the hunt to discover what evil is afoot.

After rising to prominence for his role investigating the case of Jack the Ripper, former Detective Inspector Daniel Wilson is now retired. Known for his intelligence, investigative skills, and most of all his discretion, he's often consulted when a case must be solved quickly and quietly. So when a body is found in the Egyptian collection of the Fitzwilliam Museum in Cambridge, Wilson is called in.