What goes into a query letter?

In looking at my submissions pile this month, there seems to be a great deal of confusion as to what a query letter should consist of.

A query letter has:
• A brief outline of the plot. This is where you define and clarify the protagonist, villain, and conflicts. Anything more than a paragraph, and you’re giving me the synopsis.
• Word count
• Genre
• Brief bio

How do you outline your plot?
• Who is the protagonist?
• What dilemma does he face?
• Important plot twists?
• How does it get resolved?

If you introduce a ton of peripheral characters that aren’t key in explaining the plot, you’re going to lose me. This is a lot like Dragnet; just the facts, m’am.