Evil Once Begun takes place on historic and picturesque Mackinac Island, Michigan, in its Upper Peninsula. It combines the tourist lure of rugged scenery, history, and lovely lakes with mystery woven around stolen antique jewels, murder, and romance. The Chief of Police on this small island has his hands full trying to keep the peace between locals, worried about murder"s effect on the tourist trade, state officials arriving to investigate, and his ill-equipped staff"s excitement. Then there is the lovely widow he wishes wasn"t involved.