The Secret Detective Agency Books in Order

The Secret Detective Agency series shifts Helena Dixon's mysteries into the Second World War, trading 1930s hotel life for blackout curtains, air raid sirens and the coded paperwork of Whitehall. At its heart is Jane Treen, an efficient War Office administrator who drinks strong coffee, favours sensible tweed and owns a one eyed ginger cat called Marmaduke.

Jane's official job is to coordinate field agents and decode the steady stream of reports crossing her desk. When one case turns deadly, she is ordered out from behind the typewriter and into the field. Partnered with shy, asthmatic codebreaker Arthur Cilento, Jane finds herself unofficially running the Secret Detective Agency, a small unit set up to tackle murders that could have dangerous consequences for the war effort.

In the first book a woman with links to their work is found in a Devon lake near Arthur's country home, and what looks like a village tragedy quickly hints at treachery. Later investigations send Jane back to her childhood seaside town to probe a body on the beach, keep her in London to untangle the strangling of a government typist and return her to rural Devon when a seemingly simple tearoom murder threatens a delicate codebreaking mission.

The series blends cozy village and city locations with the higher stakes of wartime espionage. Bomb damage, rationing and rumours of spies form the backdrop, but the focus stays on people, from vicars and teashop owners to newsreaders and civil servants who may or may not be loyal. Jane and Arthur's partnership develops over the books, moving from slightly prickly strangers to a more relaxed, equal team, helped and gently scolded by Arthur's capable manservant Benson.

Readers can expect familiar Golden Age touches such as closed circles of suspects, coded diaries and carefully placed clues, along with the extra tension of knowing that a mistake might cost more than one life. Each mystery stands alone, yet there is a clear arc as the Secret Detective Agency grows, the war moves on and Jane becomes more confident away from her desk. If you like your historical mysteries with a dash of spycraft, a hint of romance and plenty of tea and coffee, this series is designed to scratch that itch.