EXCLUSIVE: Steve Martin is joining the cast of the Ang Lee-directed Billy Lynn’s Long Halftime Walk for TriStar. Martin will join newcomer Joe Alwyn, with Garrett Hedlund in line for another key role. The adaptation of the Ben Fountain novel starts shooting in April.

In the film, Bravo Company, and 19-year-old private Billy Lynn, survive a harrowing Iraq battle that is captured by news cameras. They are brought home by the U.S. administration for a promotional tour, culminating at the spectacular halftime show of a Thanksgiving Day football game, all while facing an imminent return to the war. Almost the entire movie takes place during the day of the game, with flashes back to the underlying events and Billy’s heroism.

Martin is repped by WME and attorney Michael Gendler.