The Rose and the Ghost - Locke & Steel, #2

THE CITY OF LIGHT CASTS A DARK SHADOW. After fleeing the Agency, Hazel and Steel travel to France on the trail of the demon who killed Steel's family. Their only clue leads them to Paris, and to rumours of a mysterious spectre terrorising the opera house. As they begin investigating, they're confronted by members of the French paranormal agency, the Sûreté. Faced with the looming threat of arrest, Hazel will have to keep the agents from discovering why she fled England while trying to find and catch the opera ghost before they do. Yet the memory of Rayne's death haunts her dreams.
With guilt shadowing every decision she makes, she can't tell which path is the right one - or who she should trust.