Geniuses come in all shapes and sizes, including that of an 11-year-old boy named Henry Carpenter (Jaeden Lieberher). As the man of the house, Henry has taken on more responsibility than the average elementary-school student: He helps his single mother Susan (Naomi Watts) with her finances and general life problems, and serves as a guardian and mentor for his playful younger brother Peter (Jacob Tremblay). He's also well-known around town for his uncommon intellect and down-to-earth personality, choosing to remain at his local school (instead of taking classes for gifted students) and refusing to let his overdeveloped IQ get in the way of providing others with various forms of support.
When unexpected circumstances arise, Henry is forced to give his mom a detailed plan he's developed to help his neighbor and classmate Christina (Maddie Ziegler), who's being abused by her seemingly upstanding citizen of a stepfather (Dean Norris). The responsibility now falls upon Susan to expose this dangerous secret, with the help of Henry's da Vinci-esque creativity and unwavering sense of social justice. In his own way, this genius child is able to make a positive impact on the lives of everyone he knows, while proving that they are stronger individuals than they give themselves credit for.
Throughout this emotional roller coaster of a plot, screenwriter Gregg Hurwitz touches on such ideas as the loss of innocence, the development of one's self-worth, and the hard truth of mortality. While the story frequently depicts Henry as a familiar brand of artist-engineer savant, his interest in the importance of human relationships provides a fresh approach to the archetypal role of the child genius. Rather than basking in the glory of his unique abilities, Henry brings out the best in others due to this aptitude for emotional understanding.
The movie's thoughtful portrayal of its characters is further accentuated by the personal growth each one experiences through numerous challenges and twists of fate; time and again, they're forced to make difficult decisions for the greater good, which is never easy. The result is an inspiring and believable tale that is sure to make any audience wish they had known this special young man in real life, demonstrating that a role model is defined by his or her actions rather than by physical stature. In The Book of Henry, it isn't what one leaves behind, but how one helped others during life, that represents a person's legacy.