Sophie Taylor and Lilian Rose are agents with the British Secret Service Bureau.
Okay, officially they are the two founding partners in the Taylor & Rose Detective Agency but they will come to find one of their most steady 'clients' is the new and highly secretive intelligence organization.
But first we should back up a bit. And to set the stage best it is important to note that these adventures all take place shortly after the start of the 20th Century. Exactly when I cannot say but I would postulate around 1905.
Taylor is a young woman likely just nearing 18 years old who is thrilled albeit scared to have landed a job in the Millinery Department of Sinclair's, a just-opening huge emporium on Piccadilly Circus eponymously named after a rich American. Her military father had recently died in an accident in South Africa and she was out of funds so she was taking her first steps into the workforce.
Rose is slightly younger, probably 16, who comes from a very well-off family and having a desire to make her name in the entertainment industry as a singer and actress but is also supplementing her income by working as a fashion model at Sinclair's; not being beholden to her family meant not having to asceed to their demands as to her life plans.
The two will meet on their first day and will hit it off beautifully which is good because Taylor will need a friend when she is in the wrong place at the wrong time and is suspected of being part of a major jewelry theft. They will join forces, along with Billy Parker, apprentice porter, and Joe (last name unknown) who works in the stable yard when not having his hand in things a tad less legal.
Their work to solve that mystery will lead to more work on more mysteries and then an offer to help out a private investigator named McDermott who has ties to that Secret Service Bureau and through him now so did they. Which is how when Taylor and Rose decided to open their own agency, at the strong suggestion and financial backing of that rich Sinclair. And it is how the Bureau would find their skills and abilities too good to ignore.