When Elizabeth II ascended the throne in 1952, the monarchy and the Parliament wondered just how her rebellious younger sister, Princess Margaret, would fit in. Would the extroverted party girl push the Royal Family into crisis? Or would this boundary-pushing princess pave the way for future generations and turn a backward-looking country on a path forward? The answer to both questions was a resounding yes. Beyond the tabloid headlines through letters written to and by Margaret throughout her colorful life, we reveal the astonishing stories of a remarkable woman.