While the title riffs on a superhero movie, “Captain Fantastic” is as far from one as you can get. It’s a challenging, moving story of a father and his family, and while his particular child-rearing methods are extreme, this bittersweet tale is fascinating for anyone puzzling out the decisions you make as you raise your family. Quirky, funny and thought-provoking, “Captain Fantastic” also features great performances from Viggo Mortensen, Frank Langella and all six of the kids, particularly George MacKay as the oldest.

The best moments in this film, now playing at the Crescent Theater, are the most complex; this story of a father determined to raise his large family off the grid is most profound when it leaves questions unanswered.

Mortensen as Ben, the father, often makes a compelling case for his hardcore version of homeschooling, but throughout the film also makes the case against it. While Ben hammers into his children a denial of the “establishment,” he is in many ways brainwashing them too. It’s just a different script.

The rollercoaster begins immediately. We go back and forth between thinking the poor kids are deprived to thinking they live in an unspoiled Eden, as they read classic books by the fire then break into a joyous all-family singalong. But a shadow hangs over their life, in the form of their absent mother.

She is in the hospital for clinical depression, her wealthy, disapproving family footing the bills, and almost immediately we get the devastating news that she has killed herself. Is their family system ideal if the matriarch expels herself from paradise?

This tragic event propels the family, in their homemade outfits and riding in a school bus named Steve, into the real world. Driving to their mother’s funeral, against the express wishes of her parents, the kids are exposed to the novel concepts of cola, grocery stores and video games.

Their various interactions with the outside world add depth to the portrayal of their unusual lives. On the one hand, they are extremely intelligent; on the other hand, some of their activities are positively dangerous. They steal food from the grocery store, but the oldest son gets accepted into every single Ivy League college.

The push and pull plays out in the film, and emotions run high when they attempt to fulfill their mother’s wishes for her funeral. Her parents, meeting some of their youngest grandchildren for the first time, make Ben’s lifestyle choices look even more complicated. Langella’s character is a parent, too — burying his only child. It’s not black and white.

“Captain Fantastic” will make you think, laugh and definitely cry. It’s a sweet but not saccharine family saga. And while Viggo Mortensen’s Ben may be fantastic, he’s far from perfect, and the film is all the better for it.

“Captain Fantastic” is now playing the Crescent Theater.