The Midpoint or One Hour Turning Point
About an hour into your film things get real. During the midpoint, or One Hour Turning Point, the protagonist begins to change, but has a false victory. At the same time, the antagonist raises the stakes.
There's a few different ways of how you can set the midpoint up, there's the false ending and the false victory. A false ending is where you tease the audience thinking the movie is almost over, like take Into the Woods for example. The characters have all found their happy endings and then all of a sudden a giant comes down from the sky! It's kind of like saying to your audience, "But wait, there's more!" Personally, in my opinion, I think it's better to have a false victory because it seems more common in movies.
Let's take a look at Back to the Future for example. The midpoint is where Doc Brown tells Marty the only way to generate enough power for him to get back to 1985 is by a bolt of lightning. Remembering the flyer from early on, Marty knows exactly when the lightning is going to strike the clock tower, which causes a false victory. To make things worse, the stakes are raised when Doc tells Marty not go anywhere or do anything for the next week, or else there could be repercussions that could alter the future. Unfortunately, Marty has began to alter the future by saving 1955 George McFly.
In "The Little Mermaid", the midpoint takes place about 45 mins in or so. It's where Ariel signs a contract with Ursula and gives away her voice, in exchange for legs. At this point in the film, not only is the antagonist one step closer to reaching her overall goal, the stakes have raised and a ticking clock is set in place. Now that she has legs, she has until the sunset on the third day to make Prince Eric fall in love with her and must have true loves kiss. So in a way, this is like a false victory for Ariel. Although she's getting her dream of being human, there's a lot more at stake in order to make her dream become a reality.
In Shrek, the midpoint occurs when Shrek and Fiona are getting along. Shrek's goal to getting his swamp back is now a false victory because now he has to choose between returning Fiona to Lord Farquad and get his swamp back, or stay with Fiona, which creates inner conflict for him. So, although things seem to be going right for him, this difficult choice raises the stakes for him.
And finally in "Eternal Sunshine of the Spotless Mind" about 54 minutes in, Joel (played by Jim Carey), yells "I want to call this off!" Clementine feels like something is wrong but doesn't know what, which creates a false victory. in order to keep Clementine in his memory, they have to find a spot in Joel's mind where the erasure process won't find her.
Personally, I love a good twist in a film and sometimes the best way to show a plot twist would be during the midpoint. Of course there are times when the protagonist seems to do well at the midpoint and the antagonist fails. If you have any questions, feel free to ask me! I'm more than happy to help out.