“Dido of Idaho,” an offbeat comedy by Abby Rosebrock at the Echo Theater Company, takes a shockingly dark turn. There are other surprises in store for the audience, but the violence that occurs midway through the play is all the more intense for the outré humor that precedes and follows this unexpected atrocity. At the center of the story is Nora (Alana Dietze), a 32-year-old untenured musicologist with self-esteem issues and a drinking problem.

She’s caught in a futile romance with Michael (Joby Earle), a married English professor at the University of Idaho whose sensitivity can make it hard to see just how manipulative he can be. He’s been promising Nora for a while that he’s going to leave his wife, but something always prevents him from taking this momentous step. Nora is starting to worry that she’s being played, but Michael has a way of coaxing her past her suspicions.

She wants to believe in his goodness, but the real issue is that she just can’t imagine her sad, penurious life without him. The play, presented in the round in a characteristically vibrant Echo Theater Company production under the acute direction of Abigail Deser, starts with Nora and Michael in bed listening to an aria in Henry Purcell’s opera “Dido and Aeneas.” This piece of music doesn’t bode well for Nora’s future.

Dido’s love for Aeneas, of course, ends tragically, with Dido killing herself after her beloved abandons her to fulfill his destiny as the founder of Rome. Mich.