Historian William Dalrymple journeys to Morocco, Turkey, Syria and Pakistan to explore whirling dervishes, Qawwali singing and other forms of music sacred in Sufism, the branch of Islam that emphasizes music as a mystical route to the holy. Capturing performances of renowned Muslim musicians such as Rahat Fateh Ali Khan and Sain Zahoor, the film reveals that at the heart of Sufism lies a dedication to tolerance and pluralism.