The play’s engine having finally turned over, it purrs confidently to the end, which includes a coup de théâtre reminiscent of the one in Hunter’s previous Signature outing, “A Case for the Existence of God.” Like that gorgeous play, too, it offers the idea of incremental hope to those whose lives would not seem to allow it. The trick, as Stacey learns from reading medieval history, is to find the freedom in that. There is no fate, Hunter argues, and his play demonstrates: just an infinity of second chances.