HBO Nightingale poses a challenge to its viewers from its opening scene on. Protagonist Peter Snowden (David Oyelowo) has done a terrible thing—only hints of the aftermath can be glimpsed on screen—and the audience is trapped in his house with him. The film, which premieres on HBO Friday, is an audacious one-man show—a series of deluded, sometimes charming, often tragic, occasionally frightening monologues delivered by a troubled veteran clearly in the midst of a dissociative crisis.