Per Variety, "Monster" will mark Smith's stateside acting debut, and he will star as the male lead for the film.
Outside of "Dr. Who," Smith has very few film credits to his name - British titles like "Womb" and "Bert & Dickie," e.g. - so the decision to cast him probably had a little something to do with his popular (and zany) work in TV. Given the surreal subject matter of the movie, Smith's experience muscling through wacky material to make it work will come quite in handy.
"How to Catch a Monster," based on Ryan Gosling's own twisted script, follows Billy, a single mother of two existing in a dark, vanishing city who then gets swept into a hellish underworld while her son discovers a pathway to an underwater village.
Smith is one of only two attached castmates so far who's not previously worked with Ryan Gosling - the other being Rob Zabrecky. Meanwhile, Christina Hendricks, who co-starred with Gos in "Drive," is expected to fill the Billy role, while Ben Mendohlson and Eva Mendes, both of whom appear alongside him in "The Place Beyond the Pines," have also been cast for the film.
Production on "Monster" is expected to start in May.