This well-written adventure musical transports us to a medieval countryside through a variety of clever means. The costumes, of course, but also the accompanying instruments. Michael Gordon Shapiro’s arrow-and-bow stratagem is to structure his music to convey the flavor of his time and place. The performers, too, bite off funny speeches and well-wrought lyrics with rustic aplomb. And then there’s the stagecraft, the set of inventive devices that make us believe in horses and monsters and jailbreaks. This is sheer showmanship on a postage stamp stage: both in the writing and the presentation, there are great gobs of good ideas.