This one is going to be a bit tough.  There are a couple of avenues that can be tried.  The enotes links on Tagore feature many answers that give plot summaries on the story.  Additionally, the short story criticism page on Tagore does have a brief plot summary.  The web search idea is a good one, but I am not sure you are going to get a plot summary as much as you will get writings on the story that focus on a specific element of the short story, as opposed to a straight plot summary.  I know this sounds trite, but it is a very short story and one of Tagore's most direct.  It might not be a waste of time to actually read the story.  It moves fairly quickly, as the voice of Tagore in establishing the village and the postmaster is punctuated with his description of Ratan and her interaction with the postmaster. Once the postmaster gets sick and Ratan takes care of him, it is more than halfway done, setting up the ending where she is abandoned by the postmaster who goes home to his native Calcutta.  I would probably suggest reading it only because I am not sure a plot summary is going to hit the philosophical power of the ending, where Tagore essentially makes the argument that the breaking of another's heart is an inescapable pain both for the one who was broken and the one who broke it.  It is this philosophical ending that is missed in most summaries, reason enough to read it, in my opinion.