"Mighty Oak" is a portrait of Dr. Oakleigh Thorne, II, an extraordinary environmental pioneer, transformative educator, joyful musician, and an effective, inspirational leader. The wonder and reverence that Oak sees in the natural world has been a guide through his life. Starting as a child he explored the wild woods of Long Island, often as a photographer or filmmaker. As a teenager he was mentored by a Native American cowboy at a ranch in Wyoming where they would travel on horseback to remote wilderness areas. The experience radically changed the course of his life. He moved on to create non-profit organizations such as Thorne Films, Thorne Ecological Institute, Thorne Nature Experience, and achieved successes in land preservation through community action across the country that preceded the EPA and much of the modern environmental movement. He has directly and immeasurably contributed to the environmental education of hundreds of thousands of youth. His enduring legacy is a significant contribution to the environmental movement and to those he has inspired along the way. This extraordinary 93 year old man continues to mentor young people and spread an environmental consciousness, and with his astounding musical skills, still plays the piano and arranges a cappella music for choral groups. The filmmakers who both have a personal friendship with Oak, followed him for several years as he spread wisdom and joy in his journey through life, whether it be with the music of a bird or the human voice.