Adams plays Susan, who owns an art gallery in Los Angeles, and has an ex-husband who wants to be a writer. Her current husband is a doctor (Arnie Hammer), but he travels a lot, leaving Susan in a void while he’s away and being unfaithful.

One day Susan receives a copy of a novel that Tony, her ex (Gyllenhaal), has sent. As she reads it, the story of the novel is dramatized for us. Tony has taken his connection with Susan and converted it into a fictional family highway trip that turns lethal when marauders launch an assault and a life and death struggle begins.

Gyllenhaal also plays the lead character in the film portions of the novel, which upon reading Susan finds scary and too close for comfort and deeply unsettling. We watch the playing out of the story in the manuscript, which unfolds as in an old Hollywood noir film. The double-barreled treatment makes “Nocturnal Animals” suspenseful and absorbing, as well as shining a spotlight on Susan’s life and that of her former husband.