Literary agents can be very specific in how they think a query letter should be pitched. 
Rather than leading with the plot, lay out the case for your book in a crisp, tidy four-paragraph format that begins: 1) Here is a (describe type of book), 2) It’s the story of (give only a three-sentence summation), 3) Here’s how the book came to be written and what people think of it, 4) Here are my credentials.
Others aren’t as encouraging: No unsolicited queries accepted.
