What Maisie Knew is a contemporary New York City revisioning of the Henry James novella by the same name, written by Carroll Cartwright and Nancy Doyne. It revolves around unwitting 7-year-old Maisie (Onata Aprile), caught in the middle of a custody battle between her mother Suzanna (Julianne Moore), an ageing rock star, and her father, Beale (Steve Coogan), a major art dealer.
In a race to win the court's advantage, Beale marries Maisie's nanny Margo (Joanne Vanderham), prompting Suzanna in turn to marry friend and local bartender, Lincoln (Alexander Skarsgård). Both forced into a battle neither wishes to be a part of, Margo and Lincoln come to empathize with Maisie's position and over time with one another. Teased by the notion of making their own surrogate family, the trio must either submit to the will of Maisie's parents or eventually face their wrath.