Nancy

Lies can be slippery, not always the cut and dried thing we think they are but sometimes a sort of sinister mental carboot sale, where the potential believer, like an eager buyer, is just waiting with their trust in hand to be sold an untruth.

Lies are also a way of life for Nancy (Andrea Riseborough, who notched up an impressive four films at this year's Sundance). In fact, along with her dreams of becoming a writer, the creation of intricate lies is pretty much all that Nancy has. Living at home with her less than grateful mother (Ann Dowd), she writes less than successful fiction in between inventing vibrant, often damaging, 'other lives' to tell people she meets about. Her reality is as grey as the signs of old age creeping, unwelcome through her hair - and that's just one of the less overt indicators of mortality that she has to contend with.

It's not so much of a reach then, when a news story about a girl who has been missing for decades catches her eye. The age-progression image of how the kidnapped child might look now is eerily similar to her, while her childhood has evidently been less than sun-dappled, prompting her to pick up the phone.

Waiting, as they have waited for decades, at the other end of the line are Ellen (J Smith Cameron) and Leo (Steve Buscemi), whose reaction is fuelled by a destructive combination of doubt and hope. What follows is an intense character study in triplicate, made gripping both by the deliberately ambiguous way in which Christina Choe approaches everyone's mental state and by the performances. Buscemi and Cameron give achingly believable turns as a couple who might be willing to overlook a potential truth in order to find emotional peace, while Riseborough sheds every ounce of vanity, shrinking beneath Nancy's mop of hair and bedraggled sheepskin coat.

This is not a film about her being a wolf in sheep's clothing, however - Nancy can just as easily be viewed as a victim. Choe probes at the idea of being shaped by circumstance. And, as with many of the leading female characters at Sundance this year, in films as diverse as Puzzle and Colette, there's a winning complexity to Nancy that stops her from being easily pigeon-holed.

The story itself may not be quite as fleshed out as the psychological territory the characters are moving through but the situation offers Nancy the thrill of possibility and, artfully illustrates that, in some ways, the trio are driven by a shared emotion. What the veracity of the situation is becomes less important than what all three of them are aspiring to believe - and in a world full of lonely people, there's a lot of truth in that.