Amy Adams commits herself fully to portraying a mother caring for her small child while her husband (Scoot McNairy) works long hours away from home. There’s nothing to indicate he's being unfaithful, but she gradually feels worn down by the constant demands of this energetic young boy. He struggles with sleep, is always lively, and has a habit of using inappropriate language at inconvenient moments! Her concern grows when she notices unwanted hair growth and what appear to be larger teeth, leading her to wonder if she’s undergoing some kind of change. Suddenly, dogs become intensely interested in her, and she and her son begin engaging in dog-like play more often... She also experiences memories of her own mother and her unpredictable behavior. Could this be a genetic issue? Adams's acting is the highlight; otherwise, it’s an underwhelming horror story that doesn’t quite succeed. The characterizations – few characters are actually named – shift between loving mother (and occasionally wife) in a way that’s entertaining for a while, but then becomes tiresome. While her exhaustion from childcare duties is understandable, it's not fundamentally different from what any parent (male or female) might experience when dealing with an inquisitive and easily frustrated child. The depiction of their marriage feels unbalanced, as if Scoot – who missed out on significant parts of their son’s development – was having an easy time while she gave up her life and career to be the primary caregiver at home. Ultimately, once the comedic aspects faded, I found this a rather tedious film that seemed to imply this woman was exceptional among parents, and that motherhood is somehow more intense than fatherhood. The horror elements are underdeveloped, and by the conclusion, I simply felt bored. I did appreciate the artwork in her gallery; it would be perfect for a Christmas tree, and the young boy (I believe they used twins) was genuinely the best part of the movie.

Source on TMDB