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.

1929: Miss Clara Vale is a woman ahead of her time. Rather than attending Oxford to bag an eligible Duke (as her mother, Lady Vale, so desperately hoped), she threw herself into a degree in chemistry, with aspirations to become a scientist in her own right. But the world isn't ready for Clara. Unable to land a job in science because she's a woman, she is stuck behind the desk at a dingy London library. Until her estranged Uncle dies suddenly, leaving her his private detective agency, and laboratory, in his will.

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.

Hayley Burke has landed a dream job. She is the new curator of Lady Georgiana Fowling's First Edition library. The library is kept at Middlebank House, a lovely Georgian home in Bath, England. Hayley lives on the premises and works with the finicky Glynis Woolgar, Lady Fowling's former secretary. Mrs. Woolgar does not like Hayley's ideas to modernize The First Edition Society and bring in fresh blood. And she is not even aware of the fact that Hayley does not know the first thing about the Golden Age of Mysteries.

In the sleepy village of Cookingdean, Dr Nell Ward is busy working in the grounds of a local manor house. Whilst inspecting an old tunnel, she did not expect to overhear a murder. As the only person with any clues as to what happened, Nell soon finds herself in the middle of the investigation. Desperate to clear her name Nell, along with her colleague Adam, set out solving the murder using their skills as ecologists to uncover details no one else would notice. But it soon becomes clear that playing Agatha Christie is much harder than it might, at first appear.