When a body washes up on the beach, an anthropologist finds her life on the line to keep a secret that history has long forgotten.
A logline is targeted to movie producers. Taglines and blurbs are targeted to movie viewers. They are two different market audiences with two different set of interests.
The goal of tagline or blurb is to induce a viewer to lay down US$10 (and more) and invest 2 hrs of time in the finished film. And offer an expectation that she will come away with a satisfactory viewing experience.
The goal of a logline is to induce a movie producer to lay down millions of dollars and invest months of time in making the film. And offer an expectation that the movie producer will come away with a profit.
In order to reel in a movie producer, get him to even read the script, you have to bait the hook with a logline that gives him (or her) a clearer indication of what the story is about than is necessary for a movie viewer. So:
Who is the protagonist and what is her character flaw? Who is the antagonist? (Big, big casting questions.)
What does the protagonist NEED to accomplish — what is her objective goal? (Indicates the genre)
What are the stakes? What does she stand to gain if she succeeds, stands to lose if she fails? (Is it something that can engage an audience’s emotional investment in the protagonist’s struggle? IOW: can this be parlayed into a franchise?)
Hope this helps. For more info, click on the “Training” option at the top of the web page.