The Masquerade of the Marchioness — Claire Delacroix

She's not the woman he married...

Philomena Wright, Marchioness of Arlingview, is universally admired for her intellect, good sense and charitable efforts on behalf of widows and orphans. A woman with every advantage, she also has a guilty secret: in truth, she is Philomena's twin sister, Penelope. Dreading spinsterhood, she attends a masquerade ball in the hope of finding a suitor before admitting the truth—only to encounter a gentleman who stirs her like no other...

Garrett Wright misses the purpose—and the peril—of his work as a spy during the war and is bored with his disguise as a reckless rake. When he agrees to help unveil a jewel thief preying upon London society, he is beguiled by a beauty who awakens a dream—and becomes determined to unveil the truth, whatever the cost. 

When he finds stolen gems in her possession, Garrett fears his lady has a more dangerous secret than her identity. Forced to choose between honor and unexpected love, how will he both fulfill his duty and secure a happy future with the woman who has captured his heart forever?