It's a warm summer evening in Cedar County. A storm is just beginning to roll onshore from Lake Michigan. In the auditorium of the Mission Point Summer Colony, the audience settles in for a performance of a stage adaptation of Agatha Christie's Death at the Vicarage. By the first intermission the intense thunderstorm is overhead.

The old auditorium reverberates to the violent tumult. Flashes of lightning cast eerie shadows through the rolling, heavily wooded landscape. Then the power fails. The building and surrounding countryside go black.

When the electricity is restored, Ray Elkins, the Sheriff of Cedar County, is guided from his seat in the auditorium to the stage area. A member of the cast has been found fatally stabbed.