A conclusion is not merely a summary of the main topics covered or a re-statement of your research question, but a synthesis of key points and, if applicable, where you recommend new areas for future research. For most essays, one well-developed paragraph is sufficient for a conclusion, although in some cases, a two or three paragraph conclusion may be required.
New Insight, Not New Information!
Don't surprise the reader with new information in your conclusion that was never referenced anywhere else in the paper. If you have new information to present, add it to the discussion or other appropriate section of the paper. Note that, although no actual new information is introduced, the conclusion is where you offer your most "original" contributions in the paper; it's where you describe the value of your research, demonstrate that you understand the material that you’ve presented, and locate your findings within the larger context of scholarship on the topic, including describing how your research contributes new insights or value to that scholarship.
Conclusions. The Writing Center. University of North Carolina.