Wandering Souls follows the mounting of a new stage production, Bangsokol: A Requiem for Cambodia, to honour the nearly 2 million Cambodians who died during the Khmer Rouge regime from 1975 to 1979. Commissioned by Cambodian Living Arts, the Requiem is a first-time collaboration between filmmaker Rithy Panh and composer Dr. Him Sophy. The film tracks the story of the Cambodian creators and musicians, as they work with an international team to bring the production to the world stage. Alongside the evolving stage production, the film tells the first-hand survival stories of the Cambodians involved in the Requiem, and their powerful will to reclaim an artistic heritage that disappeared during the four years of Pol Pot terror.