Series numeration from Fantastic Fiction.

"Bow Street agent Sebastien Wolff, Earl of Mowbray, doesn't believe in love--until a passionate kiss with a beautiful stranger in a brothel forces him to reconsider. When the mysterious woman is linked to an intrigue involving a missing Russian princess, however, Seb realizes her air of innocence was too good to be true. Princess Anastasia Denisova has been hiding in London as plain 'Anna Brown'. With a dangerous traitor hot on her trail, her best option is to accept Wolff's offer of protection--and accommodation--at his gambling hell. But living in such close quarters, and aiding Wolff in his Bow Street cases, fans the flames of their mutual attraction. If Anya's true identity is revealed, does their romance stand a chance? Could a princess ever marry a rogue?"--Provided by publisher.