The Midpoint of a story isn’t just a bookmark slipped into the center of a screenplay, short story, or novel. It’s quite possibly the most important plot point in the entire story, yet it’s also the most neglected element.
The Midpoint is where the main character stops reacting and starts acting.
Billy Wilder (attributed)
It’s often a tributary in the story where character joins plot in a pivotal moment when the protagonist or hero stops reacting to events controlling his life and decides to take control of his own destiny. In the beginning of many stories, the antagonist or antagonistic force is pushing against the main character. At the Midpoint, the main character pushes back.
The Midpoint may also give the audience a glimpse of the answer or resolution to the main character’s problem established in the beginning.
In 40 Year Old Virgin (because I happen to be staring at the DVD), the Midpoint occurs when protagonist Andy Stitzer (Steve Carrell) hits a low point after his friends set him up with a male prostitute. Deciding that he’s no longer going to react to events, Andy takes control of his own destiny, marches across the street, and asks the gorgeous grandmother (played by Catherine Keener) out on a date, thus giving the audience a glimpse or sneak preview of the story’s final resolution.
The midpoint of The Empire Strikes Back is actually a late one if you're going by pages. It's where Luke Skywalker battles the false Darth Vader in the tree cave. The scene not only signals Luke's intentions to meet Vader face to face, but it sets up the fight between father and son at the end, and even hints at the later revelation that Vader is in fact Luke's father.
In Harry Potter and the Sorcerer’s Stone the Midpoint of the book is when Harry, Hermione, and Ron discover the great big dog guarding the entrance to the hidden passageway. The final line of the chapter reads: ‘It looked as though Harry had found out where the grubby little package from vault seven hundred and thirteen was.” This introduces the second half of the story, which is working out what’s hidden in there, and how can they get to it. It also foreshadows the setting for Harry’s final confrontation.
Understanding the Midpoint and learning to use it effectively can be the key to unlocking the mysteries of plot for many writers struggling with structure.