Encountering adaptations of the myth of Orpheus and Eurydice seems as inevitable as Orpheus’s fateful turning around to look toward Eurydice on their journey out of Hades. Sarah Ruhl’s Eurydice, from 2003, is receiving a revival to conclude her Signature Theatre residency. The production is directed by Les Waters, who also helmed the play at Yale in 2006 and at Second Stage in 2007. Ruhl’s mournful and whimsical take emphasizes Eurydice’s life and point of view, hence the title excising “Orpheus and,” even bestowing its heroine with some agency, especially during that oh-so-famous moment of Orpheus looking back.