The Buggles' 1979 synth-pop hit Video Killed the Radio Star never really cried out to be considered a love song, but as an anchoring motif of Sarah Polley's new drama, it assumes a dizzy romantic power. It's the soundtrack to a thrillingly illicit affair and, crucially, assumes an entirely new significance in the final scene.
Polley, an accomplished actor with credits stretching back to when she was 6, impressed with her 2006 feature debut Away From Her, in which Julie Christie played a woman with dementia who, forgetting she has a husband, falls in love with another man.
This film treads the same territory - although it's a different kind of forgetting and a different kind of love - and if it does so with slightly less assurance, it's riskier, bolder and more satisfying.
Margot (Williams) meets Daniel (Kirby) while on a trip to a national park. Their first exchange of words is not auspicious, but things look up when they find themselves sitting together on the flight back to Toronto. By the time they learn that they are virtually neighbours, the sexual tension has already ratcheted up several notches.
If that seems improbable, it's far from being the film's only contrivance. Margot's husband Lou (Rogen) produces cookbooks of exclusively chicken recipes but the Italian standard cacciatore only makes Volume 2; Margot's early comment to Daniel that "I'm afraid of connections" is only one of several damp squib lines; Lou's recovering alcoholic sister (despite being vigorously played by Sarah Silverman) is something of a character cliche.
But much is redeemed by the heartrending authenticity of Williams' performance. I didn't much care for Blue Valentine, despite the excellent work that she and Ryan Gosling turned in, because it was such a remorseless downer and we never knew why things had turned so bad. But in this film, as Daniel turns out to be a persistent suitor, we are with Margot every step of her crazy and uncertain way.
Williams' ability to register emotion in the slightest expression is the kind of skill that comes along only a few times in a generation. With the possible exception of the strikingly similar Carey Mulligan, there's no better actress of her age now working and she's a dream to watch even when the material is problematic.
Take This Waltz - the Leonard Cohen song of the same title puts in a late and resonant appearance - loses its way quite badly in the final reel; there's a scene involving three people when you're expecting two that I never came close to figuring out, but in a sea of predictable and vapid romcoms, this is something worth getting your teeth into.
Cast: Michelle Williams, Seth Rogen, Luke Kirby Director: Sarah Polley
Running time: 112 mins
Rating: R16 offensive language and sex scenes
Verdict: Williams triumphs in a flawed but substantial film