Forget about trying to come up with an original story. You won’t and you’ll simply waste your time. However, what you can do is come up with an original way to tell a story. If you can tell a story in a unique and intriguing way, that’s far more important than trying to come up with a story that nobody has ever heard before.
There are two movies that on the surface may appear totally unrelated: “Alien” and “Shadow in the Clouds.” Yet underneath, they’re both telling the exact same story.
In “Alien,” a monster has gotten aboard a spaceship and the crew has to fight it off while trying to survive. Yet the idea for “Alien” came from a World War 2 myth that pilots of all nationalities swore was true.
During long flights, World War 2 pilots swore they saw little monsters, dubbed gremlins, land on their planes and start ripping out electrical wiring, puncturing fuel tanks, or tearing out hydraulic hoses to wreck the plane. This didn’t occur just once but multiple times with all nationalities.
Rather than describe a story about a gremlin tormenting a bomber crew during World War 2, the story of “Alien” shifted to science fiction, but the basic idea is the same where a monster gets on board a ship and starts killing the crew members one by one.
“Shadow in the Clouds” is based on the exact same story but actually depicts a World War 2 bomber crew fighting off a gremlin in an airplane. Same story but different setting. Yet that different setting along with different motivations of the characters creates a completely different story even though the plot is identical and based on the same idea.
So don’t worry about coming up with an original plot. Come up with an original way to tell the same story. Plot is far less important than creating a unique setting with distinctive characters we can care about.