I've never written a script before and the format intrigued me.
Here is my most humble submission.

The doppleganger trope is hardly original in movies, but I surmise it should make for a pretty fun exercise, necessitating clever camera tricks and the two main actors switching roles and positions when needed.

...unless your actors are identical twins, that is. That would definitely ruin the challenge!

I made sure to include a stabbing with pints of (fake) blood.

I hope you all like it.