Tilda Swinton is Margaret Hall, a comfortable mother of three who lives in a splendid clapboard house on the shores of California's exclusive Lake Tahoe.

But the first time we meet her she's just been buzzed into a gay club in Reno and is warning oily hustler Darby Reese (Josh Lucas) to stay away from her son Beau (Jonathan Tucker).

However, things spiral out of control when Darby ignores the warning and turns up at the house in pursuit of Beau.

After tempting Beau to the family boathouse, the pair scuffle and Darby falls off the pier...and is impaled on an anchor.

The next morning Margaret is walking along the beach and discovers the body: rather than tell the police her first thought is for her son and she disposes of the body in a remote cove.

However, her attempts to conceal the crime fail and it's not long before someone is knocking on her door - but it's not the law.

Alec Spera (Goran Visnjic) shows her a videotape of her son and Darby in a steamy clinch...and informs her he wants $50,000 or it goes to the police.

Based on the 1940s novel The Blank Wall, this is a superior thriller that departs from the tried and tested path when Margaret gets embroiled with her blackmailer.

Swinton's vanity-free performance provides the plot with its main drive as she frantically attempts to raise the cash.

The sympathetic Alec is caught between the desperate Margaret and his blackmail partner, the coolly ruthless Carlie Nagle (Raymond Barry).

The more he sees her desperation to drum up the readies, the more he empathises with her...and the more Carlie turns the screw.

Swinton's flawless portrayal of a mother in crisis is beautifully captured in this rarity - a thriller that dares to be different.

Tim Evans