Trained as a musician, English writer-director Sally Potter (The Tango Lesson) still thinks like one. All the dialogue in her timely masterpiece--a passionate post-9/11 love story about an unhappily married Irish-American scientist (Joan Allen) and a younger Lebanese chef (Simon Abkarian) set in London, Belfast, Beirut, and Havana--is written in rhyming iambic pentameter. Beautifully composed and deftly delivered, it becomes the libretto to Potter's visual music, creating a remarkable lyricism and emotional directness. This is a story about class and age as well as cultural difference, so it matters that the scientist's dying aunt is a communist and that her sympathetically portrayed estranged husband (Sam Neill) is an English politician. It matters even more that the action is framed by the married couple's maid (Shirley Henderson), who addresses the camera as she discusses dirt and what we think about it. R, 100 min. Reviewed this week in Section 1. Landmark's Century Centre.