Natalie Napoli is the novel’s protagonist, as well as the narrator, since the novel takes the form of science notebook that she also uses as a diary. She is a seventh-grader doing her best to remain positive and focused at school, in her friendships, and in her personal life while her mother has depression that she doesn’t discuss with her. Although Natalie has trouble officially settling on a question to investigate for science class, she unofficially chooses to investigate what’s going on with her mom: what depression is, what causes it, and how it can be treated. To do this, Natalie uses the scientific process she’s learning about at school. She also applies what she learns in science, such as information about plants and magnets, metaphorically to people to try understand what sustains and promotes life.

Through her study, Natalie comes to understand that her mother’s depression is not something that suddenly entered their lives because of a specific catalyst. Rather, her mother has depression at different times for different reasons, but it’s no one’s fault, and her mom isn’t doing it on purpose. She also learns to accept the ways that depression affects the rest of her family.