Veteran Gallic director Rivette makes very long films. The unreleased Out One lasts 13 hours, making his latest `thriller', three-hour Secret Défense, a short by comparison. Bonnaire plays Sylvie, a cancer researcher given new evidence about her dad's death. She decides to kill his business associate and successor, Walser (Radziwilowicz) as an act of revenge. But, at Walser's country estate, there are complications, not least the accidental killing by Sylvie of employee, Veronique (Marsac).
It's a twisted tale but, with its interminable shots of Bonnaire looking either anxious or contemplative, the murder-mystery unfolds too slowly. There are flashes of humour, and Radziwilowicz's character is intriguing, but despite the flurry of dramatic revelations, this is still a long haul that fails to deliver much in the way of an emotional pay-off.