As explained in the film, according to ancient texts a Hindu widow had three choices; she could join her husband on his funeral pyre, she could marry his younger brother (if available) or she could go into an Ashram (refuge) with other widows and live a life of self-denial to atone for the sin of having lost her husband.. It is the third option Chuyia (Sarala) takes on the death of her husband in 1938. Chuyia however is only nine years old and scarcely remembers getting married.
The Ashram is a poor place, self-supported by the proceeds of begging and prostitution, but there is camaraderie amongst the women (who are of all ages) and Chuyia, initially, is not badly treated. The focus shifts to Kalyani (Lisa Ray) the Ashram's "jewel" who becomes involved with a young political activist Narayana (John Abraham), a supporter of Gandhi.
The film is not so much an attack on religion as on particular beliefs. I've no doubt one could live the life of a devout Hindu without believing that widows are responsible for their husband's deaths just as one can be a devout Christian without believing in slavery, or that the earth is flat, or was created in 4004BC. Although the film is set just prior to World War 2 there are undoubtedly many supporters of the ancient texts still out there Mehta was prevented from filming in India by some of them and "Water" was eventually filmed in Sri Lanka. I find it impossible to have any sympathy for their position because it really amounts to using the practices of a society which has long passed away to defend an economic interest, or rather to excuse the abandonment by her family of a woman who has had the ill-luck to lose her husband. As Chuyia asks, where is the Ashram for the widowers? Also, whatever could be said for child marriage on social or economic grounds 2000 years ago, there is no possible justification for it now.
It's a great pity the film was banned in India and Pakistan it is a film for the citizens of those countries rather than me, but it is striking to watch and I suspect, not easy to forget.