Roy Batty is the leader of the renegade Nexus-6 replicants. He is very intelligent, fast, and skilled at combat, and yet still learning how to deal with developing emotions. He leads a few of his fellow replicants on what is inevitably a fruitless search for more life. As hope slowly fades away and his friends are eliminated one by one, it is his experience that brings up the question of "What is human?"
The "prodigal son" of Eldon Tyrell, Roy returns to his "father." First seeking a longer life, then asking forgiveness, he ultimately destroys his own maker.
There is no future for Roy, as his friends are killed, his hope for more life is quoshed and finally his girlfriend, Pris, is "retired" by the Blade Runner Rick Deckard.
After he plays cat and mouse with Deckard, he performs an act suggesting perhaps that he has gained the empathy that is the thin dividing line between the Humans and the Replicants. Showing more "humanity" than the men who seek to kill him, we are left wondering at what exactly makes us human.