In “Youth Without God,” a high school teacher in an unnamed German town watches as his pupils uncritically absorb fascist dogma. He looks on with a mixture of disgust, helplessness and, mostly, inertia. When a student dies on a camping trip, he is forced to make a moral choice that has unforeseen consequences for the murder trial that ensues.

In a departure for Mr. Ostermeier, who is known for startlingly contemporary productions, in which actors frequently break the fourth wall during their sweaty, acrobatic performances, the Salzburg production features period costumes and props. The few modern accouterments include some live video projections and onstage microphones, into which several actors whisper the teacher’s inner thoughts.

The novel “Youth Without God” is closer to an existentialist parable than an anti-Nazi manual, something that Mr. Ostermeier, who makes no hero of the teacher, clearly understands. Mr. Hartmann invests the role with stubbornness and vulnerability, and gives an ambivalent, not especially likable performance.

Horvath himself was no stranger to moral quandary and compromise. Even after he had relocated from Germany to Austria in 1933, the writer struggled — and failed — to reassure the Nazi regime of his respectability. By highlighting the teacher’s isolation and indecision, Mr. Ostermeier suggests a parallel between the author and his protagonist, both of whom react to external circumstances with indecision and cowardice.

It is one of the more interesting and involved ideas in a stage adaptation (by Mr. Ostermeier and Florian Borchmeyer) that otherwise seems faithful to a fault. Compared with other recent versions of “Youth Without God,” including Zeno Way’s in Stuttgart and Nurkan Erpulat’s at the Maxim Gorki Theater in Berlin, the Salzburg production comes across as stifled.