The most disturbing moment of this movie is right before the credits start to roll, with a list of Philip K. Dick's loved ones who died or became seriously ill from drugs. This is the beginning of his Author's Note, which appears abridged in the movie:
This has been a novel about some people who were punished entirely too much for what they did. They wanted to have a good time, but they were like children playing in the street; they could see one after another of them being killed - run over, maimed, destroyed - but they continued to play anyhow.
A Scanner Darkly paints a dystopian future (1994 in the novel, the movie seems to be set in an unspecified but near future), where a considerate portion of the population is addicted to drugs - specifically Substance D, an immediately addictive drug that eventually and leads to psychosis and death. ("D... Substance D. "D" is dumbness, and despair, desertion-desertion of you from your friends, your friends from you, everyone from everyone. Isolation and loneliness... and hating and suspecting each other, "D" is finally death. Slow death from the head down.")
The story follows law enforcement efforts to fight the infrastructure that produces and deals the drugs, and a community of addicts that consumes them. They are linked through Robert Arctor (Keanu Reeves), an undercover detective who has infiltrated a community of drug users and is trying to find a distributor by becoming close to Donna (Winona Ryder), a small-time dealer. He slowly loses his sense of self - he is required to wear a suit that scrambles his appearance to remain anonymous, and starts to disassociate the person he sees on the endless hours of surveillance tape from himself, especially when he starts to consume more and more Substance D.
Reading the novel, I found it hard to imagine that anybody would find the visual language to translate Dick's ideas into a movie, and in that regard, Linklater (and the rotoscope technique he uses, colouring over existing material) succeeds completely. He finds a haunting language for the (often inadvertently comical, though not less tragic) hallucinations, and it's perfect for Arctor's loss of self within the suit.
What does a scanner see? Into the head? Down into the heart? Does it see into me, into us? Clearly or darkly? I hope it sees clearly, because I can't any longer see into myself. I see only murk. I hope for everyone's sake the scanners do better. Because if the scanner sees only darkly, the way I do, then I'm cursed and cursed again. I'll only wind up dead this way, knowing very little, and getting that little fragment wrong too.
Subtly, the story also examines and questions what kind of methods are justifiable in this "war against drugs", and whether it is moral to expect these kind of sacrifices from one individual for an undefined greater good, considering that the war on drugs, as David Simon argued so well in The Wire, can never be won. A Scanner Darkly is more interested in the human costs than questions of policy, and only hints at the massive industry behind the production of drugs, and how, in this version of the future, it is linked to the equally as successful industry that treats those who fall victim to them. Ultimately, it's about the broken man who has lost everything he once had, including his sense of self, in a field of flowers, and the woman in a café wondering if the end justifies the means.
2006, directed by Richard Linklater, starring Keanu Reeves, Robert Downey Jr., Winona Ryder, Woody Harrelson, Rory Cochrane.