Have a look at books on writing films.
One thing I like to do is consider the plot in its most basic form and then think of a story of my own that follows that plot. This isn't new. Plots are recycled all the time. I have a book about Silent Movies in which the business of recycling plots by changing settings and times was a big job for writers of the time.
Try this -
Think of a film you like
Write the plot out in a series of 10-15 sentences.
Use the plot line to construct a story of your own, set in another time and place.
Use a bit of writerly skill to make it difficult to see at a glance the film you got your idea from.