Verity Kent is a former agent with the British Secret Service.
As a 'former' operative Kent was fully expecting that all the work she did for that organization would be behind her, and she would be right - sort of. She will discover that the experiences she had and the training she received, especially in the field where her life depended upon learning quickly and correctly, would make her far more attuned to what was happening around her and that, plus a natural curiosity that cannot be quelched, will cause her to get involve in more than one event touching upon the old days. Throw in the contacts she made as an operative which she will find use for in these new mysteries, and Kent will never be fully out of the 'game' and never out of the danger.
The timeframe for the Kent activities start at 1919. The Great War was just recently concluded and with it the need for her putting her life on the line. We learn soon after meeting her that she had not long ago said goodbye to her war-time clandestine work and returned to the life as a member of the wealthy upper-class in England. That should have meant that she would be spending most of her time lazing about or taking part in charitable endeavors for the less fortunate but as indicated before, that is not the case. Yes, there will be considerable hobnobbing with the titled gentry and other such but she is no longer able to not spot when things are not so perfect as they seem on the surface.
Kent is a young widow - likely in her early 20s - who had fallen in love with the handsome and fascinating Sidney Kent and as the rest of England was heading off to war in 1914, she, at the age of 18, agreed to marry him. A short engagement followed by a very short honeymoon and then he was gone off to the horrid trenches and she was left needing something to do. That is when she went to work as a secretary and translator for the covert organization no one ever actually referred to as the Secret Service. This would lead to increased involvement in the operations of that group and eventually to "clandestine assignments I'd taken on later in the war, traveling into war-torn Belgium and France".
Within a short time we will learn that Sidney is not dead - the reasons for the subterfuge playing major roles in their lives thereafter - and the days of putting her life in peril are far from over.