There are 4 books in the The Agency series. The newest book is Rivals in the City which came out in 2015.

1
A Spy in the House

Book cover of A Spy in the House
A colourful, action-packed Victorian detective novel centred around the exploits of "agent" Mary Quinn.

At a young age, Mary is rescued from the gallows by a woman masquerading as a prison warden. She is taken to Miss Scrimshaw's Academy for Girls. The school, Mary learns, is a front for a…
When you buy books, we may earn a commission that helps keep our lights on (or join the rebellion as a member).

2
The Body at the Tower

Book cover of The Body at the Tower
Mary’s second adventure as an undercover agent forces her to relive some harrowing childhood experiences as she seeks the identity of a murderer.

Mary Quinn is back, now a trusted member of the Agency, the all-female detective unit operating out of Miss Scrimshaw’s Academy for Girls. Her new assignment sends…

3
The Traitor in the Tunnel

Book cover of The Traitor in the Tunnel
Get steeped in suspense, romance, and high Victorian intrigue as Mary goes undercover at Buckingham Palace — and learns a startling secret at the Tower of London.

Queen Victoria has a little problem: there’s a petty thief at work in Buckingham Palace. Charged with discretion, the Agency puts quickwitted Mary…

4
Rivals in the City

Book cover of Rivals in the City
In a tale steeped in action, romance, and the gaslit intrigue of Victorian London, Mary Quinn’s detective skills are pitted against a cunning and desperate opponent.

Mary Quinn has a lot on her mind. James Easton, her longtime love interest, wants to marry her; but despite her feelings, independent-minded Mary…