The Lost Soul by Gabriella Pierce

Jane Boyle has long since known that her mother-in-law is evil, but she'd never imagined Lynne Doran was actually the embodiment of a powerful, ancient body-snatching demon. Now that Jane has uncovered 666 Park Avenue's dark truth, she must race against the clock to find a way to destroy Lynne before she finds her next unwilling host. As Jane attempts to tap into powers stronger than her enemy's, her estranged husband, Malcolm, arrives in time to join the fight . . . but can she possibly learn to trust him again—before it's too late?