In every screenplay, the first 30 minutes contain exposition that explains what the story its about and what the hero wants to achieve. Then in Act II (the next 60 minutes), the hero sort of gets what he or she wants, but there’s a catch and that catch is irony.
In “Up,” the old man wants to escape from being sent to a nursing home so he ties balloons to his house and floats away from the people who are about to take him to the nursing home. The ironic catch is that he also has a stowaway, a Boy Scout who was trapped on his front porch when the house floated away. Now the old man is free but he has to deal with this Boy Scout.
In “10 Cloverfield Lane,” a woman wakes up to find herself trapped in an underground shelter, run by a man who claims there’s been a disaster outside and he saved her. When she plots her escape and is nearly out the shelter door, she’s on the verge of freedom until she meets a woman outside the shelter door trying to get in because there really was a disaster outside.
In “Don’t Breathe,” a woman breaks into the home of a blind man to rob him. She succeeds to get in with her friends, but now that she’s incised, the irony is that the blind man has locked them all inside his house and he starts hunting them down one by one.
The key twist in Act II is that the hero gets what he or she wants, but there’s a huge ironic catch and that ironic catch is what drives Act II.
Think of “Star Wars” where Luke finally escapes from his planet, except now he’s being pursued by Imperial stormtroopers. That ironic catch drives the rest of the story.
The transition between Act I and Act II is that the hero must enter a new world, but that new world has an ironic catch. If the hero enters a new world, it’s just a change of scenery, but an ironic catch makes that new world suddenly more dangerous, creating a problem that the hero must solve.
In “Up,” the old man has to resolve his relationship with the Boy Scout. In “10 Cloverfield Lane,” the woman has to resolve her relationship with the man who really did save her life and locked her in an underground shelter. In “Don’t Breathe,” the woman must deal with the blind man trying to hunt her down and kill her. In “Star Wars,” Luke must deal with stormtroopers trying to find and capture or kill him.
Make sure the transition from Act I to Act II contains more than just a change of scenery as the hero enters a new world. Add an ironic catch that will create new problems for the hero that will power the rest of the story to the end.