Stephen Fleming (Jeremy Irons), a high-ranking British Member of Parliament living a comfortable, quiet life with his devoted wife Ingrid (Miranda Richardson), meets Anna Barton (Juliette Binoche) at a political reception. Anna is the mysterious fiancée of Stephen's adult son, Martyn (Rupert Graves). Despite the catastrophic risk to his family and career, Stephen enters into an obsessive, secretive sexual affair with Anna. As Martyn's wedding to Anna approaches, Stephen's growing obsession and Anna's emotional detachment lead directly toward an unavoidable tragedy when Martyn uncovers the truth.