The screenplay, written by Hampton Fancher and David Peoples, is loosely based on the novel Do Androids Dream of Electric Sheep? by Philip K. Dick. The film features Harrison Ford, Rutger Hauer, Sean Young, Edward James Olmos, M Emmet Walsh, Daryl Hannah, William Sanderson, Brion James, Joe Turkel and Joanna Cassidy. The lead art designer was Syd Mead, and the soundtrack composer was Vangelis.
The film describes a future in which genetically manufactured beings called replicants are used for dangerous and degrading work in Earth's "off-world colonies." Built to be 'more human than human', they appear physically identical to humans — although they have superior strength and agility — while lacking comparable emotional responses and empathy. Replicants became illegal on Earth after a bloody mutiny. Specialist police units — blade runners — hunt down and "retire" (i.e. kill) escaped replicants on Earth. The film primarily focuses on a particularly brutal and cunning group of replicants hiding in Los Angeles and a semi-retired blade runner, named Rick Deckard, who reluctantly agrees to take on one more assignment.
Blade Runner initially polarized critics; some were displeased that it hadn't the pacing expected of an action film while others appreciated its thematic complexity. The film performed poorly in North American theaters but achieved success overseas. Despite poor early ticket sales, it was embraced by fans and academics and became a cult classic. Its popularity as a video rental made it one of the first films to see a DVD release. Blade Runner has been hailed for its visionary production design and credited with prefiguring important themes and concerns of the 21st century. It remains one of the most singular variations on the film noir genre and observers continue to see its myriad influence on culture. Blade Runner brought author Philip K. Dick to the attention of Hollywood, and several films have since been made from his writings.
Note: The following synopsis refers to the "Director's Cut" version of the film.
In Los Angeles, November 2019, Rick Deckard (Harrison Ford) is called out of retirement when a fellow Blade Runner — Holden (Morgan Paull) — is shot during a Voight-Kampff test by Leon (Brion James), an escaped replicant. Tyrell dimming the sun Enlarge Tyrell dimming the sun
A reluctant Deckard is brought to his old boss Bryant (M. Emmet Walsh), who informs him that the recent escape of Nexus-6 replicants is the worst yet. Deckard resists getting involved but relents after Bryant threatens him enigmatically.
Bryant briefs Deckard on the replicants: Roy Batty (Rutger Hauer) is a commando, Leon a soldier and manual laborer, Zhora (Joanna Cassidy) a sex worker retrained as an assassin, and Pris (Daryl Hannah) a "basic pleasure model." Bryant also explains that the Nexus-6 model has a four-year lifespan as a failsafe against their developing unstable emotions. Deckard is teamed up with Gaff (Edward James Olmos) and sent to the Tyrell Corporation to ensure that the Voight-Kampff test works on Nexus-6 models. While there, Deckard discovers that Tyrell's (Joe Turkel) young secretary Rachael (Sean Young) is an experimental replicant (who believes she is a human) with implanted memories from Tyrell's niece, which provide a cushion for her emotions.
Deckard and Gaff search Leon's apartment as Roy and Leon force Chew (James Hong), an eye designer, to direct them to J.F. Sebastian (William Sanderson) who can lead them to Tyrell. Later, Rachael visits Deckard at his apartment to prove her humanity to him, but leaves in tears after Deckard recites several of her most secret memories and states they were not her memories at all, but were implanted. Pris meets up with Sebastian and takes advantage of his loneliness and kind nature to gain access to his apartment.
Clues from Leon's apartment lead Deckard to Taffy Lewis' (Hy Pyke) bar where the tattooed Zhora is performing with a snake. Zhora attacks Deckard and makes a desperate attempt to get away into the crowded streets; Deckard chases her down and "retires" her. After the shooting, Gaff and Bryant show up and inform Deckard that Rachael will also need to be "retired". Deckard conveniently spots Rachael in the distance, though as he follows her he is suddenly disarmed by Leon who then proceeds to beat him. Rachael kills Leon, saving Deckard's life, and they go back to Deckard's apartment where they discuss her options, and in a rough scene ending in musical intimacy they begin to fall in love.
Meanwhile, Roy arrives at Sebastian's apartment and they convince Sebastian to bring Roy to meet Tyrell. Once in Tyrell's bedroom Roy demands an extension to his lifespan and requests absolution for his sins from the Godlike replicant creator; upon receiving neither he kills Tyrell and Sebastian. The Bradbury Building Enlarge The Bradbury Building
Deckard is sent to Sebastian's apartment and is ambushed by Pris, though he manages to shoot her after a struggle. Roy returns moments later, trapping Deckard in the apartment and playfully hunts him throughout the dilapidated Bradbury Building, eventually forcing him to the roof. Deckard attempts a jump to another building and ends up desperately hanging from a beam. Roy easily makes the jump and stares down at Deckard — just as Deckard loses his grip Roy grabs his wrist and saves his life. Roy is deteriorating quickly (his 4-year lifespan is up) as he sits down in the rain and eloquently marvels at the highlights of his life and concludes, "All those moments... will be lost... in time... like tears... in rain. Time... to die." Roy quietly dies as Deckard looks on in silence. Gaff arrives in a spinner shortly afterward and, as he's leaving, cryptically shouts, "It's too bad she won't live. But then again, who does?"
Deckard returns to his apartment and cautiously enters when he sees the door is ajar. He finds Rachael alive and as they leave Deckard comes across an origami calling card left by Gaff; he has allowed them to escape, and they depart toward an uncertain future together. 
Despite the initial appearance of an action film, Blade Runner operates on an unusually rich number of dramatic levels. As with much of the cyberpunk genre, it owes a large debt to film noir, containing and exploring such conventions as the femme fatale, a Chandleresque first-person narration (removed in later versions), and the questionable moral outlook of the Hero — extended here to include even the humanity of the hero, as well as the usual dark and shadowy cinematography.
It is one of the most literate science fiction films, both thematically — enfolding the philosophy of religion and moral implications of the increasing human mastery of genetic engineering, within the context of classical Greek drama and its notions of hubris — and linguistically, drawing on the poetry of William Blake and the Bible. Blade Runner also features a chess game based on the famous Immortal Game of 1851. (The king and queen are interposed on Tyrell's side, a position which a grandmaster would never attempt.)
Blade Runner delves into the future implications of technology on the environment and society by reaching into the past using literature, religious symbolism, classical dramatic themes and film noir. This tension between past, present and future is apparent in the retrofitted future of Blade Runner, which is high-tech and gleaming in places but elsewhere decayed and old.
A high level of paranoia is present throughout the film with the visual manifestation of corporate power, omnipresent police, probing lights; and in the power over the individual represented particularly by genetic programming of the replicants. Control over the environment is seen on a large scale but also with how animals are created as mere commodities. This oppressive backdrop clarifies why many people are going to the off-world colonies, which clearly parallels the migration to the Americas. The popular 1980s prediction of America being economically surpassed by Japan is reflected in the domination of Japanese culture and advertising in LA 2019. The film also makes extensive use of eyes and manipulated images to call into question reality and our ability to perceive it.
These thematic elements provide an atmosphere of uncertainty for Blade Runner's central theme of examining humanity. In order to discover replicants, an empathy test is used with a number of questions focused on the treatment of animals, thus making it the essential indicator of someone's "humanity". The replicants are juxtaposed with human characters who are unempathetic, while the replicants appear to show passion and concern for one another at the same time as the mass of humanity on the streets is cold and impersonal. The film goes so far as to put in doubt whether Deckard is a replicant, and forces the audience to reevaluate what it means to be human.
Is Deckard a replicant?
Among fans of the film, the question of whether Deckard is human or replicant has been an ongoing controversy since the film's release. Ridley Scott, after remaining coy on the subject for twenty years, stated in 2002 that Deckard is a replicant. Hampton Fancher and Harrison Ford, however, have stated that Deckard is human. The rough consensus among fans is that in the original version of the film Deckard is probably human, whereas in the Director's Cut he is a replicant. Specifically, the Director's Cut shows a dream of Deckard's that features a unicorn; when Gaff leaves Deckard an origami unicorn at the end of the film. This suggests Gaff knew about the dream and implies that Deckard is, like Rachael, a replicant with implanted memories.