The huge and enduring popularity of John Lennon's song 'Imagine' is examined in this documentary. Yoko Ono, who is now acknowledged as the co-author of the song, is filmed as she continues her mission to spread Lennon's message using "any means I can". Analysis of the song's power - the lyrics are shown to be appreciated by people with different beliefs - also includes contributions from academics, and psychiatrist Raj Persaud even goes so far as to claim the song fills the void left by the decline in organised religion. There's also space given to detractors, including journalist Robert Elms, who openly detests the track.