When Lions Roar begins in the mid-1930s at Chartwell, Winston Churchill´s country estate, with new revelations surrounding a secret business deal orchestrated by Joseph P. Kennedy, the soon-to-be American ambassador to Great Britain and the father of future American president John F. Kennedy. From London to America, these two powerful families shared an ever-widening circle of friends, lovers, and political associates – soon shattered by World War II, spying, sexual infidelity, and the tragic deaths of JFK´s sister Kathleen and his older brother Joe Jr. By the 1960s and JFK´s presidency, the Churchills and the Kennedys had overcome their bitter differences and helped to define the “greatness” in each other.