In 2019, humans have genetically engineered Replicants, which are essentially humans who are designed for labor and entertainment purposes. They are illegal on earth, and if they make it to our planet they are hunted down and killed.
Rick Deckard is a blade runner, a hunter of replicants. A group of replicants makes it to Los Angeles seeking a way to extend their life span. Replicants have a built-in 4 year life span, and this group is near the end.