Lord of Lies by Amy Sandas

Portia Chadwick knows she’ll never have a life of adventure. But when a dangerous moneylender kidnaps her sister, Portia seeks help from a man known only as Nightshade. Soon she finds herself charging headfirst into his world of intrigue and danger―and unexpected passion.

Dell Turner grew up in London’s back alleys and gin lanes. Vowing to escape his low beginnings, he hires himself out to society’s elite. When he accepts a job from a beautiful young lady, he doesn’t anticipate her relentless determination to join his mad occupation…or her unnerving ability to inspire emotions he thought long buried. She’s as dangerous to him as his world is to her, and yet Dell can’t bring himself to turn Portia away… even if it means risking her life.