The idea of Viggo Mortenson as a father raising a tribe of kids in an off-the-grid self-sufficient lifestyle hints at something really interesting and, whilst there are some really enjoyable moments in Captian Fantastic, ultimately the film fails to fully realise the potential of the premise. That is not to say this is a bad movie because there is much to like, but it just seems as though writer/director Matt Ross has taken the easy option in the interests of trying to mould an unconventional story about unconventional characters into something that will still satisfy those viewers who like their film narratives to follow a somewhat predictable and, dare I say, happy trajectory.

Deep in the forests of Washington State, Ben Cash (Mortenson) is a devoted father, committed to raising his six kids with a rigorous physical and intellectual education. The children do not go to school, but they are very intelligent, albeit without any understanding of how the world works beyond the regimented routine that Ben has instilled in them; hunting, physical training (in various forms from gruelling runs, to mountain climbing to hand-to-hand combat) and reading (philosophy, literature) are the staples of each day. They do not celebrate Christmas, instead choosing to celebrate events such as Noam Chomsky’s birthday because, unlike Jesus or Santa Claus, Chomsky is real and important. Ben’s wife Leslie (Trin Miller) has been hospitalised, forcing the family to embark on a road trip aboard the Partridge Family-style bus that is their only means of transportation. The tension of the story lies in the conflict between Ben and his father-in-law Jack (Frank Langella) about the way in which the children are being raised. Much argy-bargy ensues as the arrogant, wealthy Jack threatens to have the children removed from Franks care. It’s hard to delve into much more detail without giving away key plot developments, but in Ben and Frank, Ross has constructed two alpha male characters that could not be any more different.

Even though we only ever see Leslie in flashbacks/dream sequences, she is very much at the core of the tensions as Frank holds Ben responsible for the circumstances that have led to her hospitalisation. In that regard, the film fails as an exploration of mental illness as it descends into nothing more than two men at loggerheads about what is best for a woman who is never really given any voice of her own. Frank is a reprehensible construct whose superciliousness is too extreme to be taken seriously and Langella’s considerable talents are wasted on a character whose every action is driven by jealousy and an overwhelming sense of superiority. He wants to take the kids from Ben as revenge for what has happened to Leslie. To be fair, Ben is also a somewhat extreme character, but at least he is driven by a genuine desire to protect his family from a world that he sees as toxic; socially, politically and environmentally. Much like Harrison Ford’s Allie Fox in Peter Weir’s Mosquito Coast, in his efforts to protect his children, Ben might actually be putting them at risk.

Cinematographer Stéphane Fontaine presents the north-west landscape as both menacing and majestic, while Ross’s music choices are unconventional, mostly diagetic and absolutely inspired. A funeral scene that might typically play out as a moment of sombre reflection is actually a moment of uplift and inspiration through the use of Guns n Roses’ Sweet Child O’ Mine. Mortenson is perfectly cast in the lead role and delivers another typically solid performance, while the six young performers – George Mackay, Samantha Isler, Annalise Basso, Nicholas Hamilton, Shree Crooks and Charlie Shotwell –  are universally impressive as the Cash children, whose ages range from 8 to 18. As the oldest, Mackay’s Bodevan has the biggest narrative arc as his desire to attend college is in conflict with Ben’s views on formalised education, but all of them enjoy moments in the spotlight. Kathryn Hahn and Steve Zahn also feature as the sister and brother-in-law who represent the exact type of banal, vacuous existence that Ben is so desperate to avoid. Amusing, emotional and thought provoking at times, Captain Fantastic is an entertaining romp that is let down by the compromise of the ending, seemingly with an eye to the mainstream of which Ben would want no part.