A study of the perils of nostalgia, Megan Griffiths' Lucky Them itself comes off as a throwback to an earlier era of low-key, whimsical US independent cinema. This is not a bad thing, considering the talents of the cast – led by Toni Collette as Ellie, a hard-drinking Seattle rock critic whose glory days, like those of the magazine she writes for, are far behind her.

As unemployment looms, Ellie reluctantly accepts an assignment that involves tracking down her one-time boyfriend Matthew Smith, a grunge icon who has disappeared off the map so thoroughly no one knows if he's alive or dead. For elaborately contrived reasons, Charlie (Thomas Haden Church) tags along on this quest. He's a deep-voiced, stiff-shouldered dot com millionaire who now fancies himself as a documentary filmmaker.

Lucky Them is not really about grunge, or only incidentally. In no sense edgy, it's a traditional odd couple comedy where the strengths are in the acting and the writing. Both Ellie and Charlie start out as stock types, but their shared adventure gives them the chance to reveal hidden facets and surprising perspectives to us and to each other – so that we come to see them as people who would be worth getting to know.

Indeed, the screenplay by Emily Wachtel and Huck Botko has a screwball streak that lets even minor characters come out with intriguing non sequiturs – as when Charlie acquires a fiancee in the form of a ditzy animal-rights activist (Ahna O'Reilly) who announces that she wants him to "appreciate objects more".

Church has been playing super-square eccentrics like Charlie for most of his career, going back to the underrated 1990s sitcom Ned and Stacey. But he brings such imagination and enthusiasm to the task it seems strange that he isn't given more opportunities: this is the kind of droll performance you might hope to get from Will Ferrell if Ferrell were more of an actor and less of a put-on artist.

As for Collette, she's at her best here, in a role which – like her collaborations with P.J. Hogan in Muriel's Wedding and Mental – allows her tocombine broad comedy with unexpected feeling. Especially affecting are the scenes of Ellie listening to music, when her hardboiled mask falls away and we glimpse the idealistic fan she was in her youth, and deep down still is.