It's the middle of the night somewhere in West Texas, and the members of the Honey Island Swamp Band haven’t slept a wink.

They stagger out of the black 1980 Prevost tour bus they have affectionately named the “Death Star” to a line of fueling pumps at a nondescript 24-hour gas station. Amid much eye rubbing and leg stretching, an event begins to unfold so surreal to their bleary minds that the...