INNARDS ON THE INTERSTATE, HeIsComing Theatre Company, at the Playground. First the facts: late one summer afternoon, on Interstate 80/94 near Gary, a truck braked to avoid hitting another vehicle and spilled its cargo–lamb entrails–all over the highway. From the bare, uh, bones of this incident Jeff Grafton has fashioned a play filled with mystical manifestations, in which the ovine offal and the human body concealed within it are less bizarre than the personnel sent to investigate the accident. These include a fire marshal who fears his duties will make him late for his dance lesson, a waste-disposal engineer whose name–Peter Pore–inspires the investigating state trooper to alliterative discourse, an assistant who curses in tongues, and of course the driver of the truck, who sees biblical import in these events.