The siblings are trained in martial arts, rock-climbing and undergo a PT workout that would put the SAS to shame. In the evening they read books their father has assigned to them, ranging from Dostoyevsky to particle physics: "I'm going to quiz you on M-theory tomorrow." Bodevan denies he is a Trotskyite: "Only a Stalinist would say Trotskyite. I'm a Maoist," his father is corrected. However, when their absent mother Leslie (Trin Miller) dies, their world is completely rocked. Ben announces the news with a straightforward honesty that smacks of brutality: "Your mother's dead. She killed herself." Rellian blames his father and another crack appears when it's revealed that Bodevan has secretly applied to and been accepted by a host of major universities. The children are also appalled to hear that Jack (Frank Langella), Leslie's father and their grandfather, is planning a Christian funeral.
Although initially reluctant, Ben loads up the family bus (named "Steve") and the group head off to New Mexico in time to pull off "Operation: Rescue Mother". The predictable clash of cultures is pulled off with real flair and the oddness of the family begins to look less bizarre when compared to the freakishness that passes for 21st century American normality. "What's wrong with the people dad? Are they ill?" one of the children asks when they visit a bank. "They're all fat." A trip to a diner, a supermarket and a tussle with a traffic policeman are all managed with wit and there are some great comedic moments as the family operate as a trained, revolutionary cadre. In order to escape from the policeman they pretend to be Christians, wryly assuming some fanaticisms are more accepted than others - lambs dressed as wolves, indeed. Despite their weapons training and the real knives they receive on "Noam Chomsky Day" - their version of Christmas - there's never any real sense of danger. Rather, the family is a school of fish out of water and their naiveté is obvious when Bodevan has his first kiss in a trailer park, or the next morning when Ben greets the day in the buff: "It's only a penis," he tells a passing elderly couple.
Things become markedly more serious when they arrive at the funeral. Here they have to confront Leslie's parents and the possible fact that their lifestyle is no longer sustainable as all the forces of reaction line up against them. Up until this moment, the film's critique of 'normality' has been so devastatingly effective that any attempt at resolution smack of compromise. Unable to settle on a satisfying ending, Ross opts for several. This niggle aside, Captain Fantastic is a slickly made comedy with a witty, politically articulate script and some wonderful cinematography by former Jacques Audiard regular Stéphane Fontaine. The children are School of Rock funny and Mortensen is wonderful in the title role, showing himself a light hand at comedy. In fact, it soon becomes apparent that the title of the film is not as ironic as initially suspected. Perhaps it is a superhero movie after all.
The 69th Cannes Film Festival takes place from 11-22 May 2016. Follow our coverage here.
John Bleasdale | @drjonty