Assume that your reader is already familiar with the text. Do not repeat the plot or simply describe the text. Instead, subordinate quotations and paraphrases to your argument.
Very rarely, you will see literary critical articles that do need to narrate the story or paraphrase a text. If a text is new, newly discovered, rarely studied, or discussed outside its normal context (e.g., as a source for a later work), it may be necessary to offer a summary in order to give the reader of your argument enough information to read knowledgeably. Generally, though, you may assume that your professor is your principal reader and that s/he knows the text well.