Moonrise Kingdom, Wes Anderson, 100 mins, 12A

We can expect great things of Cannes – but not, it's a safe bet, too many laughs. You think the likes of Michael Haneke are here to amuse us? So, we'd best grab our merriment while we may, with Wes Anderson's opening film Moonrise Kingdom. Anderson's precise aesthete humour isn't to all tastes. But if it's not his best (that's surely The Royal Tenenbaums), Moonrise Kingdom is Anderson's most enjoyable film for a while. Following his animated Fantastic Mr Fox, it's the second time that Anderson has let out his inner child – in this case, his inner boy scout.

Moonrise Kingdom is essentially a children's film – at least, mature kids of an arty and knowing disposition. It's a tale of amour fou between two 12-year-olds, against the background of a scout camp. In 1965, on the island of New Penzance, precocious loner Sam Shakusky (Jared Gilman) decides he wants to leave 55 Troop, run by Edward Norton's well-meaning if martinettish scoutmaster. Off Sam stalks into the wilderness, briar pipe in mouth, Davy Crockett hat on head, to elope with moody, kohl-eyed Suzy Bishop (Kara Hayward), for whom he fell when she was playing a raven in the local pageant of, of all things, Benjamin Britten's Noye's Fludde.

The couple don't exactly travel light – their baggage includes a gramophone, a Françoise Hardy record and Suzy's kitten, plus a stock of tinned cat food. But their love, and orienteering skills, keep them one step ahead of a posse – which includes Bruce Willis's melancholy local cop, Suzy's parents (Frances McDormand, Bill Murray) and a fearsome lady in a blue uniform – named only as "Social Services" and played by Tilda Swinton. Also headed in the kids' direction is Hurricane Maybelline – a catastrophe we're tipped off about at the outset by a Thornton Wilderesque narrator, played by Bob Balaban in red duffel coat and woolly hat, looking like an auxiliary crew member from Anderson's The Life Aquatic.

You know from the first shot that you're in the rarefied realm that is Wes World: the film starts in Suzy's home, half lighthouse, half Heath Robinson construction, with the camera forever shunting sideways or panning to reveal ever odder symmetries and surprise tableaux. Like all Anderson films, Moonrise Kingdom is itself an elaborate doll's house, but this is also a poetic landscape film, with Robert Yeoman's camera exploring woods, fields and beaches to create an outward bound venture as American as Mark Twain. But the film's singularity comes from its mix of frontier spirit with a rather European sensibility – hence the Françoise Hardy record that the kids dance to on the beach, as prelude to a tentative but never too coy love scene. Hence too, alongside Hank Williams, lashings of Britten on the soundtrack, A Midsummer Night's Dream bolstering an increasingly eerie elemental mood.

As usual with Anderson, there's a huge amount of meticulous detail (he's blessed with terrific collaborators in Robert Yeoman and designer Adam Stockhausen). The muted sight gags display sublime grace: watch the scene where the runaways dive into the sea from opposite ends of the frame. Arguably, the characters are no more rounded, in the conventional sense, than the puppets in Fantastic Mr Fox. But they live because Anderson casts actors with presence, whom

you relish spending time with. He's made real finds here in young leads Gilman (whose piping voice contrasts with Sam's emergent Hemingway machismo) and Hayward, all taciturn intensity. Moonrise Kingdom may not prove Anderson's most substantial or enduring film, but as a fanciful summer excursion, it's a treat. Oh, and if you've ever wanted to see Harvey Keitel in khaki shorts and knee socks, this is your chance.

'Moonrise Kingdom' is out on Friday

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