A Scanner Darkly: Philip Dick

Substance D - otherwise known as Death - is the most dangerous drug ever to find its way on to the black market. It destroys the links between the brain`s two hemispheres, leading first to disorentation and then to complete and irreversible brain damage.

Bob Arctor, undercover narcotics agent, is trying to find a lead to the source of supply, but to pass as an addict he must become a user and soon, without knowing what is happening to him, he is as dependent as any of the addicts he is monitoring.