In a future society in the era of indefinite eugenics, humans are set on a life course depending on their DNA. Young Vincent Freeman is born with a condition that would prevent him from space travel, yet is determined to infiltrate the GATTACA space program.
A parasitic alien soul is injected into the body of Melanie Stryder. Instead of carrying out her race's mission of taking over the Earth, "Wanda" (as she comes to be called) forms a bond with her host and sets out to aid other free humans.