Scorched - The Dark Forgotten, #2

Welcome to the Castle. The price of admission is your soul. Ex-detective Macmillan always had a taste for bad girls, but his last lover really took the cake-and his humanity. Now half-demon, Mac's lost his friends, his family and his job. But Constance, a vampire trapped in the supernatural Castle prison, needs his help. Her foster son has been kidnapped and imprisoned where no creature of darkness can go.
Mac has a case to work-one that embroils him with a love god, a mad sorcerer, an even madder city council. The trail leads deep into the supernatural prison, and Mac soon learns that cracking the case will cost him his last scrap of his humanity. Fiery, vulnerable Constance will do anything for those she loves, including Mac. He'll be damned if he turns his back on her .