If you are not using post excerpts for any other purpose, you could use the built in WordPress manual excerpt feature to store your one sentence post summaries, and then change the search page to display the post excerpt instead of the full post content.
1) Nowadays the post excerpt box is hidden by default. On the Post edit page, click screen options in the upper right corner and put a check in Excerpts. That reveals the excerpts entry box. When a manual excerpt exists on a post WordPress will display that rather than the default first 55 words of the post, when an excerpt is being displayed.
2) If you want to have the Visual Editor on the excerpts box (its optional - you can use HTML tags in the box without the editor) install this plugin
3) Then you have to edit your search results template and replace
the_excerpt(); There may be code between the parentheses of the_content() - that's fine. Its not needed with the_excerpt(). If you are not too familiar with editing code the best bet is make a backup copy of the search template before you change anything so if you run into issues you can go back to how it was before you changed it.
Here's an old article about manual excerpts.
You really don't need an additional plugin to do this (other than possibly the visual editor plugin I mentioned).
This should get you started.