In unwavering commitment to his role in László Nemes’ harrowing competition title Moulin, up-and-comer Félix Lefebvre slept in the grizzly, mattress-less cell he and co-star Gilles Lellouche were shooting in — for a good few nights.

“There was bats. I didn’t have any idea what time it was. And I felt like those guys during the Second World War, [who] actually went through it and were having such a hard time,” the young French star tells The Hollywood Reporter. “I just wanted to be the best version of me, as an actor.”

To provide some much-needed context, the Hungarian filmmaker returns to the Croisette — where he picked up the Grand Prix in 2015 for Son of Saul, the film that would go on to claim him an Oscar — with the real-life story of French resistance hero Jean Moulin (played by Lellouche). It follows Moulin’s arrest in June 1943 as he attempted to reunify the forces of the Secret Army, and wound up tortured by the sinister Klaus Barbie, head of the Gestapo (Lars Eidinger).

To those unfamiliar with French World War II history, the figure might not even ring any bells. This was not the case for Lefebvre, who grew up studying Moulin. “It’s in our history class program. We hear everything about him — he’s this heroic figure, a leader of the resistance in France during the Second World War. It’s one of the things that you learn at school that you actually remember,” the 26-year-old continues, “because you hear that this guy went through the worst torture and didn’t say a word. So as a kid, you hear that, and you start thinking, ‘Well, if I went through a lot of pain, would I be brave?’ I have a very vivid memory of [learning about] this man.”

When Lefebvre — whose biggest credit to date, Summer of 85, landed him a César Award nomination for most promising actor — caught wind of Nemes’ project, he went all in. “He was watching the audition through a screen,” Lefebvre remembers. “It was this distance between him and I, and it was kind of intimidating. But then I did the first take and went really emotional … He just stood up and went closer to me and said, ‘OK, that was good. But that was too much. I think it can be great if you go more interior.’”

The more they riffed, the more impressed Nemes was. Lefebvre secured the part of Martin, Moulin’s cellmate once captured by the Nazis. “[What is] very interesting about my character is that Jean Moulin, through all the movie, is paranoid with everybody that he meets. He feels like he cannot trust anybody,” the actor explains. “Everybody around him could betray him and put the French’s future in danger. So when he meets me, we are doing these scenes in the prison that kind of feels like a game of poker — where one is trying to understand if the other one is bluffing, working for the enemy, or if he’s on your side.”

As aforementioned, Lefebvre took this game of mental poker between Martin and Jean extremely seriously. He camped out on the Budapest set — re-created to exactly match the cell the pair would have faced off in — to lose himself in Martin’s headspace, and relished being treated by acclaimed star Lellouche as a peer, not a pupil. “I always love when the great and big actors just start seeing you as a colleague,” he says. “We were really, really trying to create something together, and trying to find some truth in it together.”

It’s actually the star’s third Cannes-bound movie, though one of them, Summer of 85, was released during the pandemic, so he never made it to the Palais. In 2021, Lefebvre came with the out-of-competition Supreme, and just three years ago, premiered Delphine Deloget’s Nothing to Lose in Un Certain Regard. But Moulin, his first competition title, is particularly special: “It’s my first time [doing] the whole red carpet experience for the movie, a few thousand people watching the movie, and I’m going to discover the movie there, too.” (He has not yet seen the finished film.) “It’s going to be, I think, a very emotional moment.”

It is just one highlight from an extremely busy 2026 for Lefebvre, who has Léopold Kraus’ Microstar premiering in June and, later in the year, another movie called The Last Patient. He considers some of his dream collaborators and Paul Thomas Anderson’s name swiftly comes up, but so does Aftersun‘s Charlotte Wells and How to Have Sex director Molly Manning Walker. “Those two,” he says with a laugh about Wells and Walker, “would be the dream directors [that] I feel like I could say, ‘Hey, nice to meet you,’ at Cannes — and they would answer me!”

Before he gets to mingling with European cinema’s hottest auteurs, he must first receive his roses for Moulin. It’s no less than he deserves after that particularly method cell stay: “After a few nights, I slept so bad that I was like, ‘OK, I also now need to sleep to be able to do my job correctly.’ ”