An exemplary piece of verité film-making, Kim Longinotto's moving and insightful documentary profiles Brenda Myers-Powell, a former prostitute who runs the Chicago-based Dreamcatcher Foundation, an organisation that mentors and supports sexually exploited women and at-risk youngsters.

At times, the film seems like a chronicle of suffering but there is a tenderness and humour that belies the grim subject matter. Longinotto follows the inspirational Myers-Powell on her nighttime rounds of the city and in classrooms where she shares her experiences.

Among the most colourful subjects is Homer, a dapper former pimp, reformed and one of Myers-Powell's allies. Her interview with him is one of the few times we are aware of the unobtrusive Longinotto's presence – and we begin to realise what guile and patience it must have taken her to catch all this footage.