A Scanner Darkly is, quite simply, Linklater's masterpiece. The story is a brilliant puzzle of truth and identity amongst characters that are slowly losing both due to their drug addictions. It’s an insightful character study, a compelling mystery, and covers themes familiar in Dick’s work – from social problems to the reality of consciousness.
The look of the film is marvelous to behold and is made all the more captivating because the style has substance. The interpolated rotoscoping, animation created over Hi-Def video, creates an alternate reality, setting it apart from our own while at the same time creating the sensation of characters’ altered states.
The main character is Bob Arctor, an undercover officer in Orange County, California of the near future. To avoid collusion and corruption, everyone’s identity in the division is a secret, so his superiors know him only as Agent Fred. Assisting in the anonymity is a device called the scramble suit, a “shroudlike membrane” that masks the voice and projects on its outer surface a constant cycle of partial images of faces and bodies. Arctor is working to discover who is responsible for the influx of Substance D, a powerful psychoactive drug that causes severe paranoia and can induce shared hallucinations. Habitual use causes the hemispheres of the brain and the user’s consciousness to separate.
As a consequence of his work, Arctor himself has become an addict because “there are no ‘weekend warriors’ on the D. You’re either on it, or you haven’t tried it.” His investigation has not taken him outside of his circle of fellow users. Most apparently reside in the house where Arctor used to live with his wife and kids. He gets his supply from Donna, who is his girlfriend, although she doesn’t like being touched because of all the drugs she does. As Arctor’s drug use increases, the reality he experiences becomes less and less reliable. Not a good thing, especially when there’s legitimate reason for paranoia as your house is under continual video surveillance, your superiors test you for Substance D use, and someone from your circle is making reports to the police.