City of Light and Sun. The Order of the Crystal Daggers, #3.5

Everyone has dreams. PARIS, 1874. Benedict Svoboda knows what it means to experience loss. After the death of his mother, the rejection of his father, and the loss of his mentor, Ben is determined all the more to protect those in his care-and none more so than his beloved wife, Marguerite. However, Marguerite is no stranger to espionage. Having worked with Lady Penelope Ollerton-Wellesley and the Order of the Crystal Daggers for many years, Marguerite is able-and perhaps too eager-to work with Ben on his various missions, despite his objections.
After arriving in Paris to oversee the signing of the Second Treaty of Saigon, their mission is soon interrupted by the theft of a priceless painting-and Ben is the primary suspect. Now, to find the true culprit and prove his innocence, Ben must work with Marguerite, even as they realize not all is as it seems, and there is more danger yet to face .