After divorcing her ex-husband Tony (Jake Gyllenhaal), Susan (Amy Adams) married a man named Horton (Armie Hammer). Although the two have been married for more than ten years, it is clear that the relationship has already lost its passion and exhaustion. At the same time, the crisis encountered by Horton has brought this once wealthy family to the brink of bankruptcy, and Susan's serious insomnia continues to trouble her life. One day, Susan received an unexpected email. Tony sent his new unpublished novel "Nocturnal Animals" to Susan. He told Susan that this was a novel written specifically for her, hoping that she could read it. In the process of reading the novel, Susan constantly recalled the process of her and Tony falling in love to breaking up. In the process, some dirty and unknown secrets gradually surfaced.