Sometimes things are not always what they seem, especially in the small suburban town where the Carpenter family lives. Single suburban mother Susan Carpenter (Naomi Watts) works as a waitress at a diner, alongside feisty family friend Sheila (Sarah Silverman). Her younger son Peter (Jacob Tremblay) is a playful 8-year-old. Taking care of everyone and everything in his own unique way is Susan’s older son Henry (Jaeden Lieberher), age 12, whose creativity is without limits. Protector to his adoring younger brother and tireless supporter of his often self-doubting mother – and, through investments, of the family as a whole – Henry blazes through the days like a comet.
Susan discovers that the family next door, which includes Henry’s kind classmate, 12-year-old Christina (Maddie Ziegler), has a dangerous secret – and that Henry has devised a surprising plan to help. As his brainstormed rescue plan for Christina takes shape in thrilling ways, Susan finds herself at the center of it.