But both projects are based on the same true events.

Stranger Things type TV Show network Netflix

A filmmaker is accusing Stranger Things creators Matt and Ross Duffer of ripping off his idea for Netflix’s sci-fi hit series.

In a new lawsuit, Charlie Kessler explains he made a short film called “Montauk,” about government experiments. The film premiered in 2012 and won an award at the Hamptons International Film Festival. Kessler claims he pitched the idea to the Duffer brothers in 2014 at a party at the Tribeca Film Festival for a series called The Montauk Project, and later “presented materials” from their representatives detailing the project. Then the Duffers sold Stranger Things to Netflix in 2015 under the Montauk title.

Stranger Things was originally set in Montauk, Long Island, but the show changed its setting to Indiana (and filmed in Georgia).

Kessler’s original Montauk outline has several story beats that echo Stranger Things: A young boy who disappears, a cop with a haunted past vows to find him, there’s mysterious conspiracy at a nearby military base that’s conducting secret experiments on children, and a monster that’s created by a portal to another dimension that resembles the child’s toy.

But here’s a wrinkle that might work in The Duffer Brothers’ favor: The short film is based on a real-life conspiracy theory about Montauk involving secret paranormal government experiments at the base in the 1970s. Stranger Things was reportedly originally inspired by the same events that inspired Kessler’s film, and then became a show stuffed with tropes from all sorts of pop culture classics.

Kessler is demanding both monetary damages and a jury trial. Netflix and the Duffer Brothers had no immediate comment.

UPDATE: The Duffer Brothers issue statement blasting Kessler’s lawsuit.