Fallow by Jordan Hawk

Between the threat of a world-ending invasion from the Outside and unwelcome revelations about his own nature, Percival Endicott Whyborne is under a great deal of strain. His husband, Griffin Flaherty, wants to help—but how can he, when Whyborne won’t tell him what’s wrong?

When a man from Griffin’s past murders a sorcerer, the situation grows even more dire. Once a simple farmer from Griffin’s hometown of Fallow, the assassin now bears a terrifying magical corruption, one whose nature even Whyborne can’t explain.

To keep Griffin’s estranged mother safe, they must travel to a dying town in Kansas. But as drought withers the crops of Fallow, a sinister cult sinks its roots deep into the arid soil. And if the cult’s foul harvest isn’t stopped in time, Fallow will be only the first city to fall.