Their inquiry seems doomed with no method but plenty of madness, while a family of bourgeois holidaymakers arrive for their annual sojourn. André Van Peteghem (Fabrice Luchini) and his wife Isabelle (Valeria Bruni Tedeschi) effuse about the picturesque beauty of the simple folk and the sublime landscape. Meanwhile their two daughters (Lauréna Thellier, Manon Royère) scamper about and their niece Billie (Raph) falls for the young local Ma Loute (Brandon Lavieville), who along with his father, The Eternal (played by his actual father, Thierry Lavieville), ferry the well-to-do across the water by carrying them for twenty centimes. The Eternal is so-called for his legendary feats in saving one hundred people from the sea, but he and his family haven't so much resorted to cannibalism as embraced it wholeheartedly.
A large cauldron at the back of their rustic dwelling and mother's cry of "Anyone want more foot" suggests that they are not too coy about the mystery. And here we have one of the problems with the piece. Although set up like a mix of a seaside comic postcard and a black farce, Slack Bay has none of the tight plotting necessary to pull it all off: the mystery is not a secret; the police so bumbling as to be negligible. Instead, we're left with a fairly basic if sporadically funny comedy of grotesques. Machin is 'hilariously' fat and squeaks as if his flesh is made of over inflated balloons. Andre is a hunchback who hobbles around in a pair of knee-high leather boots, his hands fluttering in fey gestures of salutation. Binoche appears as Billie's overly theatrical mother, who is subject to drowning the scene with her cries, but is all too easily distracted. Gravity plays a large part in Dumont's comedy and a lot of people fall over, are punched in the face or, in a memorable scene, crash a land boat into a shipwreck and are catapulted through the air.
Everything is shot immaculately: the costumes are exquisite and the seascapes are enough to give Turner the vapours, while some of the performances are tone perfect caricatures of brutal mimicry. Yet each sketch is prolonged a pratfall to long, the slapstick hits a slump and many moments are repeated. Although it's exhilarating to see Binoche let rip and dial up her histrionics to atomic proportions, it begins to grate like the headmistress' comedy turn at the school disco. With obvious influences from the cinema of Roy Andersson, the effect is a similar smiling at the cleverness of it all - the artistry behind the buffoonery - rather than the more appropriate belly-laughs Slack Bay's dark material requires.
The 69th Cannes Film Festival takes place from 11-22 May 2016. Follow our coverage here.
John Bleasdale | @drjonty