Everyone in the movie business has earnestly learned to call film-makers “storytellers”, despite the fact that film-makers don’t necessarily have to deliver conventional narrative and that so many of them are in any case no good at the old-fashioned business of storytelling.

But this last point certainly doesn’t apply to Italian director Paolo Strippoli who has brought to Venice an uproarious edge-of-the-seat gripper in which Valeria Bruni Tedeschi gives us the funniest performance of the festival and the best of her career.

It’s a satirical nightmare about a wealthy woman’s Faustian bargain, like one of Roald Dahl’s Tales of the Unexpected – as elegantly designed and beautifully shot as anything by Paolo Sorrentino and with smart, subversive things to say about body image and body fascism and about a cosseted, self-involved Italian matriarch who eternally congratulates herself on sacrificing herself – or wanting to sacrifice herself – for her children.

At the centre of this bizarre drama is Anna (superbly played by Jasmine Trinca) who is complacently marred to wealthy alpha-male Bari businessman Walter (Adriano Giannini): they have two children: Alice (Romana Maggiora Vergone) and Tobia (Andrea Genovese). Each family member gets a chapter.

At a spectacular party at their gorgeous home, whose clear purpose is to make friends and neighbours jealous, a terrible accident happens, just after the children discover an ominous spiral of ants in the grass.

While praying desperately for a miracle, Anna is visited by “L’estranea” of the film’s Italian title, the mysterious stranger hilariously played by Tedeschi, who appears to know all about this rich, picture-perfect family and offers to solve their problems. But she wants something in return, a sadistic deal that cuts to the heart of both parents’ selfishness.

Anna had always wanted to act in her youth but her father forbade it – now she has been obsessively pushing Alice into acting and is morbidly upset at any physical problem that Alice has which damages this proxy ambition. As for macho Walter, he is thrilled at Tobia’s skills at football, and sponsors his son’s youth team; he is disgusted (rather than compassionate) at a weight issue that Tobia has which gets him dropped from the side.

And all the time Anna sombrely considers the sacrifices she has secretly brokered for other people to make with this smirking, skittish Mephistopheles in order to keep her family safe. But has she done wrong? Is she guilty of some obvious sin which is being punished? No. It is just a deadpan tale of supernatural cruelty meted out to someone whose only crime is smugness, vanity and being rude to her domestic staff. It all climaxes in an apocalyptic finale: an enjoyable and macabre family affair.