[Note: After learning some new information, we’ve provided some updates to this post.]

10 Cloverfield Lane did not begin as a Cloverfield sequel or anything remotely related to the 2008 smash hit. It started as a small movie from Portal fan film director Dan Trachtenberg with the working title Valencia. This was the plot synopsis we reported in April 2014:

“The majority of the movie takes place in an underground cellar, home to a teenage girl and a caretaker. The girl woke up in the cellar after a car accident, at which point her eerie companion tells her a nuclear attack has devastated society. The girl still hopes to escape.”

That’s pretty similar to the finished film, and although Mary Elizabeth Winstead’s character isn’t a teenager, she still wants to escape, especially because the caretaker, Howard (John Goodman), is creepy and dangerous.

[Spoilers ahead for 10 Cloverfield Lane]

The Film Stage outlined major changes between the finished film and the script. They state that the basic premise—girl wakes up in an underground shelter after a man says there’s been an attack outside, and there’s also a third guy with them. When it comes to the ending, here’s how they breakdown the differences: