Mahershala Ali and Viggo Mortensen make an unlikely pairing in the new film “Green Book”.

A new trailer for the film, which is set to debut at the Toronto International Film Festival next month, gives audiences a glimpse at the powerful road drama.

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Set in 1962, Ali stars as real life classical pianist Don Shirley who is going on a concert tour in the American South, with Mortensen playing Tony Vallelonga, the Italian-American hired to drive him from venue to venue.

The title “Green Book” refers to the guides black people travelling in the South often used to avoid dangerous spots and find safe places to stay.

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The film is directed by Peter Farrelly, famously of the Farrelly Brothers duo who made films like “Dumb and Dumber” and “There’s Something About Mary”. But while the “Green Book” trailer promises moments of humour, the film appears to be a major departure into dramatic territory for the filmmaker.