A teenage boy sits at his desk in Neuchâtel, Switzerland, brow furrowed in concentration as he reads a letter that has just arrived. The year is 1911, and Jean Piaget, only fifteen years old, has received astonishing news: his former nanny has confessed that the dramatic story he’d been told as a child – how she fought off a kidnapper who tried to snatch baby Jean from his carriage – was entirely made up. In the letter, the ex-nurse apologizes for having lied years ago to cover her own neglect. Jean sets the letter down, heart pounding. He is bewildered, even embarrassed, to realize that he possesses a detailed memory of the attempted kidnapping: the struggle, the nanny’s heroic cries, even the police officer’s uniform. Yet none of it ever happened. How could he remember something that was a fiction? Young Piaget gazes out the window at the gathering dusk over Lake Neuchâtel, his mind racing with questions. This moment – the shattering of a vivid false memory – plants a seed in him that will grow into one of the great quests in the history of psychology: an investigation into how we construct knowledge and how the mind of a child, in particular, forms its own logic of reality.