Philip K. Dick's A Scanner Darkly begins as a standard American nightmare. It is California, 1994, and society is divided between the straights in their fortified apartment complexes, and the acid-heads who are hooked on a new drug of unknown origin, substance D (for Death). Most of the detritus of the 1970s survives unchanged but surveillance technology has been advanced by the invention of the "scramble suit", which reduces the appearance of the wearer to a nebulous blur, and is compulsory uniform within the bounds of police headquarters. Thanks to this garment the hero, a narcotics agent turned addict, is sent on a full-time assignment to spy on himself.

From this point paranoia radiates outwards, taking us through a bewildering series of conspiratorial world-views in search of the ultimate distributors of substance D, who (the theological strain in Dick's work is becoming more marked) appear to be nothing less...