In the late 1960s, a group of North London musicians shook traditional English folk music to its roots by fusing it with rock - simultaneously outraging the purists and delighting a new and devoted audience. Through new interviews with the band including Richard Thompson, the film examines how the group survived tragedy when their drummer was killed in a car crash early in their career, followed by the tragic death of lead vocalist Sandy Denny; and how they overcame numerous line-up changes to continually reinvent themselves by discovering and recruiting some of the finest virtuosos in the country.