Theodora 'Dora' Laurent and Reginald 'Rex' Bankes-Fernsby are agents with British Intelligence.
The year we start to follow their adventures together is 1922 and in that post-Great War era there is no officially known espionage organization in the United Kingdom. Unofficially, there is the redoubtable Lord Audley, a man who was British Intelligence starting in the years before the War To End All Wars and continuing beyond its conclusion. He is not only a gifted and seasoned spymaster, as we watch we can see he is a skilled puppet-master as well. While it is important to know that Audley has considerable fondness for both Laurent and Bankes-Fernsby, he is not a bit adverse to sending them into harm's way if the cause is sufficient.
Laurent is the seasoned operative having been in the 'business' since the waning days of the War. Prior to that she had worked as a nurse near the front lines trying as best she could to ease the suffering of the English wounded or be a calming presence in a soldier's final moments. Though she came from considerable wealth and breeding, her determination to do something worthwhile drove her from the Swiss boarding school her parents, the Duke and Duchess of Dorset, had placed her to be safe from the War. She had sought the help of Audley, an old family acquaintance and frequent rival of her father. How she made the switch from a nurse bandaging war-burn victims to being an operative of Audley is told in a prequel.
Bankes-Fernsby is only just becoming an agent. He had been part of Audley's men during the War but his role was more of a courier than an operative and when the War ended, he returned to the estates of his family ruled by the impressive Dowager Duchess of Rockingham. It would be the death of his closest friend, a man who we are told was Audley's, and therefore England's, second best agent that would bring him back into Audley's circle and a new, unexpected career. That reentrance, and the subsequent spycraft training, would come from Laurent - it is no trouble then to guess who the best agent was.
Laurent is described as "every inch the femme fatale, from her strawberry blonde pin curls to her diamond-encrusted ebony earrings. Even when relaxing in her own home, she never let down her guard or her hair". She is often accompanied by Inga, an older British heiress with a Germanic name who also works for Audley, and the imposing Harris who functions as a butler for the women but who is also so much more.
Bankes-Fernsby is said to be "a handsome man, with sharp, angular features and a tall, lean frame. His hair was a pale blond, swept back in a stylish pompadour, and his piercing blue eyes were framed by long, dark lashes".
Together, with Dora as the lead but Rex proving a very quick learner, they become, as we are told in a blurb for their adventures, "England's preeminent undercover spy team".