It is reported that Satyajit Ray, a connoisseur of Western Classical Music, was continuously thinking of Mozart, while making the film. It may be interesting to analyse the film's structure in Sonata Form.
As is well known, Sonata form consists of an exposition, stating the first & second subjects, development (of secondary material, connected with the subjects) & a recapitulation. Here, Charulata (in her loneliness) may be the first subject. Her husband, Bhupati, who walks past her, immersed in his book, is NOT the second subject. However, it is his cousin, Amal, who arriving symbolically during a storm, is the second subject. Charu's brother Umapada & his wife Manda make up the household (as development material.)
After Umapada & Manda decamp with the money, Amal realises that he himself may rob Bhupathi of Charu's affections & leaves abruptly.
In the recapitulation section, the indifference of Bhupathi towards Charu (shown in the exposition section), now enhanced by suspicions of Charu's perfidy) is represented by the hands of the couple frozen apart.