Lean On Pete, the heartbreaking new film from A24 and director Andrew Haigh, is an unconventional boy-and-his-horse story, in which a young, damaged kid, played by Charlie Plummer, embarks on a journey across the Pacific Northwest with the eponymous horse to escape the hardships of his home. At the premiere of the film, we spoke with Plummer and Haigh about the experience of making the film and working with Steve Buscemi.