Isabelle Drake is the protagonist and first-person narrator of All the Dangerous Things. She is brunette, tall, and slender. She becomes an insomniac after the disappearance of her son, Mason; her inability to sleep affects her physically, as she often notes how the bags under her eyes and the brittleness of her hair have aged her significantly. In addition to her insomnia, Isabelle experienced childhood sleepwalking, as well as occasional bouts of sleepwalking as an adult. She begins the novel separated from her former boss and husband, Ben, and estranged from her parents. She is the eldest of three sisters, her younger sisters being Margaret and Eloise, and the only one to survive to adulthood.

Isabelle undergoes two journeys, both related to her identity and self-perception. The first journey is connected to her experience as a mother, while the second connects to her broader autonomy. The pain of Mason’s disappearance, exacerbated by Isabelle’s conflicting feelings about motherhood, leads her to struggle with her supposed culpability. She experiences both support and criticism from all sides, leading her to doubt herself and her maternal abilities. This questioning is paired with her search for autonomy. In Isabelle’s past, she gave up much of her identity to be with Ben; Ben’s abandonment of her, paired with new insights into his nature, leads her to search for her autonomy once again.