Runes of Lore: Dragon Dusk Book 3 (Dragon Shifter Romance) - Dragon Dusk, #3

Christine's magical life has gained her many friends and a budding romance with her dragon shifter, Tristan. One of those friends, the good Maddock, has come asking for a favor. Trouble brews in the city, and Tristan's intimate knowledge would help solve a puzzling rash of attacks. The catch is that those asking for his help don't really want it, and the mystery behind the attacks is deeper and darker than any of them realize. Tristan reluctantly agrees to take the case, and Christine and he venture to the big city of Laethion, a metropolis of magic and steam power.
There they find more foes than friends, and danger lurks in the shadows of the Alchemical Research School, the preeminent training grounds for alchemists. As they search for clues to the attacks, Christine finds herself catching hints of Tristan's mysterious past, and even shadowy future. Pieces of the dark puzzle fit together and she begins to understand not only his creation, but her own purpose.
A dark purpose that may destroy them both.