The new movie takes place in 2049 Los Angeles, where Officer K (Gosling) serves the city as a “blade runner,” an officially sanctioned bounty hunter tasked with tracking down and killing hyperadvanced androids known as replicants. Earth has been demolished by war and climate catastrophe, most plants and animals are dead, and replicants are chiefly used as slave labor for off-world colonies.
The twist is that K is himself a replicant, part of the newest generation of machines assembled with limited lifespans and behavioral inhibitors. The rogue replicants he's assigned to kill -- or “retire” in the euphemistic parlance of the day -- are older-model replicants with open-ended lifespans who rebelled against their human masters.
In the original film, Harrison Ford played Deckard, a world-weary blade runner operating 30 years earlier than the events in the new movie. The central romantic drama there was that the human cop Deckard eventually fell in love with one of his assigned targets, a replicant named Rachel, played by Sean Young.