A synopsis is a condensation or summary of a novel, a play, a tale, a story, etc. To do a synopsis the first thing is to know very well the theme you have summarize so it is important to read it completely and to reread it if it is necessary, then you have to extract the most important subject or your topic sentence, after that, it is important to identify other sentences that will reinforce your topic sentence. I generally use two or three reinforcing sentences.