Snuck out in the dog days, overshadowed by Christmas shopping and a looming Star Wars film, this bizarre entertainment deserves a prize for its sheer unreadability. Imagine the second half of Lenny Abrahamson's Room remade by the folk behind Napoleon Dynamite and you'll have some idea what to expect from Brigsby Bear. To suggest it has tonal issues would be akin to suggesting that the sea has water issues.

Is it a family film? Well, it has a scene in which a teenager shoves her hand down a grown man’s underpants. So, I don’t think so. Is it aimed at a grown-up indie audience? Only if they’re very much at home with the cute. And then there’s Mark Hamill’s character. We’ll get to that.

We begin in what might be a dystopian future. James (Kyle Mooney), a bearded man in his twenties (at least), lives awkwardly with mum April (Jane Adams) and dad Ted (Hamill) in an underground refuge amid apparent post-apocalyptic waste. His only entertainment comes from VHS tapes of a children’s show about an intergalactic champion named Brigsby Bear.

Just as we’ve taken this in, the police arrive and we learn that the couple have, in fact, abducted James as a child and Ted has created the show himself. Uneasy with his real family, despite their obvious decency, James decides to make his own sequel to the series.

There is much Michel Gondry-lite fun to be had here. Comically unaware of limits, James constructs live explosions, blurts out inappropriate remarks and fails to read messages implicit in tone or gesture. The picture is never boring and everyone involved seems impressively committed.

But little of it makes tonal sense. The protagonist is not just socially confused, he seems genuinely feeble minded. The one antagonist inexplicably changes sides for no apparent reason. Most bizarre of all is James’s eventual reconciliation with his apparently likable and charming former captor. It is one thing for the character to experience Stockholm syndrome. It’s another to ask the audience to undergo the same experience.

Unlikely to be the highest-grossing Mark Hamill fun of the season.