A tall, skinny man in blue jeans stands on a stage, one hand on his banjo, the other raised to the crowd of 15,000 people who have come to celebrate his 90th birthday. 'Come on, sing it!' he shouts, and everyone sings. How did a humble, banjo-playing Harvard University dropout become one of the most influential figures of the twentieth century? This is the story of Pete Seeger - singer, songwriter, social activist, environmentalist - who filled his toolbox with songs and set out to repair whatever in the world was broken.