Unexpected Guest (Behind Closed Doors #3)
H.H. Fowler

Meanwhile, a dashing beau from the church Gregory once led, approaches Gregory's wife, Dana, and eventually reveals his love for her. When even the police appear to believe Gregory might never be found, her hope wanes and Dana is vulnerable and unsuspecting of the beau's true intentions, which are furtively linked to the infamous House of gods.
Dana and the rest of the Beauforts remain a constant target for a secret society that will stop at nothing to ensure every member of that family is six feet beneath the soil.