The beginning and ending of a movie is very similar. In both cases, the villain is trying to accomplish something at the start and by the end of the movie, the villain is about to achieve a goal defined in the beginning. To make your story feel complete, your villain needs to initiate a goal in Act I and complete it in Act III.
Act I and Act III of your screenplay are almost identical. In Act I, the villain is trying to accomplish some goal. In Act III, the villain gets a second chance to complete the goal that he didn’t finish in Act I.
In “Star Wars,” Darth Vader would have loved nothing more than to capture Princess Leia along with the smuggled Death Star plans and then discovered the location of the rebel base to blow it up with the Death Star. However, in Act I, the villain either fails to achieve his goal or simply initiates his goal.
In “The Terminator,” the Terminator’s goal is to hunt down and kill Linda Hamilton. Ideally, the Terminator would have succeeded and that would be the end of Act I. However, Act I is where the villain often fails.
Sometimes the villain doesn’t fail but just initiates a goal. In “Die Hard,” the villain has already put the plan into action to take over the building. By the end of Act I, the villains haven’t failed, but they’re just getting started.
In “The Sting,” the villain is the organized mob that is running an illegal numbers racket. This goal suddenly gets disrupted when the hero (Robert Redford) cons the numbers runner out of $5,000. Now the villain’s goal is to kill Robert Redford.
In Act I, your villain may have failed in achieving a goal, may just be starting a goal, or may have their current goal disrupted by the hero.
Now look at Act III and that’s where the villain gets to come close to achieving his goal, which is what was foreshadowed in Act I. Act I and Act III essentially continue the same goal of the villain.
In “Star Wars,” Darth Vader wants to crush the rebel alliance in Act I and by Act III, he gets that chance.
In “Die Hard,” the terrorists want to take over the building and by Act III, they want to get away with their loot.
In “The Sting,” the organized mob boss wants to kill Robert Redford and by Act III, his hit man “torpedo” tries to kill Robert Redford.
Strip way the entire Act II and focus initially on merging the bookends of Act I and Act III together. Act I must introduce the villain’s goal and Act III must complete that goal. Act I is where the villain often fails to achieve a goal and Act III is where the villain gets his final chance to succeed.
By making your villain’s goal clear from start to finish, you’ll insure that your story doesn’t wander off into a tangent, and lose your audience in the process.