Helena Bonham Carter performs her role with nuances of visage and body, and in particular eyebrow, which capture the essence of Kate's manipulation and longing. Everyone performs well.
The cinematography is some of the most beautiful I have ever seen on film--it ranks near Vertigo as one of a few films which breach entertainment and are masterpieces of art. The Venetian and Edwardian locales never cease to fascinate and titilate the viewer. The final sequence represents graphically the vacuity which has enveloped Kate and her love with haunting realism.
Do not watch the film to be "entertained"--it depresses with little reserve and wrenches the heart. Let the music, camera, and Bonham Carter sweep you into the magic of this cinematic masterpiece.