Like many other well-reviewed films at Cannes, a robust theatrical future is by no means assured for this old-fashioned ’70s-’80s father-daughter story, which marks Penn’s first time acting in his own film, after helming six features. Thanks to Matt Damon, Penn said at Sunday’s press conference, the Oscar winner (“Milk,” “Mystic River”) finally decided to break his own rule not to do two jobs at once. “A month and half before shooting started, Matt Damon called me, not to say he could or couldn’t, but that I was a stupid schmuck not to take this opportunity to act with my daughter in this thing,” said Penn. “That was the last straw. Once I decided to do that, it was a big burden off me.”

Horberg and producer Jon Kilik had long tried to convince Penn to take the role. “Making independent films and original stories has not gotten any easier,” said Horberg at the press conference. “As a producer you dream. When I dreamed from the beginning to make the movie with Sean Penn as John Vogel, to have a real father and daughter play a father and daughter, knowing Sean’s commitment to authenticity,  this was a special way for this story to be told. We didn’t compromise. We had to fight hard to get the resources, to get Sean to do this.” When he read the book the first image Penn saw was his own daughter Dylan’s face. “In a film about deception, about the search for truthfulness,” said Penn, “it goes back to Dylan’s face. I find her uncontrived. When you can put a camera on an actor listening, that tells the whole world of truth and deception. My cinematic focus was on Dylan’s face to tell the story.”

Finally, Penn gives yet another great character performance as an unregenerate conman who loves but cannot stop lying to his daughter. Their scenes together are incendiary. Dylan Penn, whose mother is actress Robin Wright, has grown into the role over time. “I was apprehensive before I said ‘yes,’” she said. “I first read it when I was 15, and came back to it when I was 30. I could reference my own experiences and bring something to this character…He’s my father. We have a complex relationship. We’re both alpha and we can sometimes clash.” Michael Buckner for PMC Cinematographer Danny Moder leaned into the ’70s and ’80s by shooting on 16mm film. “We found our way back to a world with a slower pace,” said Moder. “We could have fun, but there was sweat and tears in it too.” Winnipeg substituted for Minneapolis. Penn’s own memories of driving cross North America since he was a kid “influenced my films,” he said. At the press conference, Penn accepted praise from American webmaster Chaz Ebert for mounting a huge testing and vaccination effort around the country during the pandemic. “Now for filmmakers and actors, we’re in a time seeing there’s an enormous price that mankind pays for not exercising its empathy for one another,” said Penn. “We were not only as a country but as a world let down and neglected and misinformed by how the truth was assaulted under an obscene administration. When my team and I would come home from test and vaccination sites, the Trump administration was maddening. The news felt like someone with a machine gun was gunning down the communities that were the most vulnerable from the White House.” When the Biden transition came, said Penn, “It felt like the sun was rising.” Speaking of which, Penn is one of many Hollywood figures including his old friends Oliver Stone (“U-Turn”) and ex-studio head and producer Mike Medavoy (“Colors”) returning to support the festival as the global film community gets back on its feet. His loyalty is strong, having won the Best Actor award in 1997 for “She’s So Lovely,” and serving as president of the jury in 2008. He’s also attended Cannes with “The Indian Runner,” “The Pledge,” “Mystic River,” “The Assassination of Richard Nixon,” “What Just Happened,” “Fair Game,” “The Tree of Life,” “This Must Be the Place,” and “The Last Face.” While “Flag Day” is a sincere and heartfelt drama that soars in the scenes between the two Penns, Dylan’s voiceover narration stops the film cold. In any case, the actress’s career is launched, and the film comes out of Cannes with a leg up in the global marketplace. That’s what Cannes does. Sign Up: Stay on top of the latest breaking film and TV news! Sign up for our Email Newsletters here.