French actor Louis Garrel pays homage here to Woody Allen’s ego by co-writing, directing and starring in a film in which two drop-dead-gorgeous women go to war over him. (Naturally, one is much younger than Garrel.)

A Faithful Man bombs the Bechdel test, of course. But it seems to me that it fails an even more basic test of humanity, since this pair of female adventurers aren’t even really characters, so much as fantasies. It’s a shame because Garrel directs with frothy light-touch flair.

The film begins promisingly, briefly flirting with an Agatha Christie-style whodunnit storyline. Garrel is Abel, a journalist who’s never recovered from his ex-girlfriend Marianne (Laetitia Casta) dumping him for his friend Paul; he pines for her with dog-like fidelity. Ten years later, when Paul dies suddenly, Abel attempts to win Marianne back. But Paul’s sister Eve (Johnny Depp’s daughter, Lily-Rose) announces that she has been in love with Abel for years. Meanwhile, Marianne’s nine-year-old son, Joseph (Joseph Engel), is telling everyone his mum killed his dad. Was Paul murdered by someone in his family? (My fingers were crossed for the angelic-faced Joseph being the culprit).

Alas, the clueing soon gives way to a drearily French ménage à trois comedy conceived by Garrel perhaps as an update of Jules et Jim. Abel moves in with Marianne. But when Eve’s behaviour becomes obsessive (in actual life, Abel would be googling lawyers to get a restraining order), Marianne is inexplicably indulgent.

What do these women see in Abel? He has good hair, but not much in the way of personality. To quote Allen: “The heart wants what it wants.”

• Released in UK cinemas on 23 August.