The semi-autobiographical story is set in a dystopian Orange County, California in the future of June 1994. The book includes an extensive portrayal of drug culture and drug use.

The title is a reference to a passage in the Bible in 1 Corinthians 13, which states:

For we know in part, and we prophesy in part. But when that which is perfect is come, then that which is in part shall be done away. When I was a child, I spoke as a child, I understood as a child, I thought as a child: but when I became a man, I put away childish things. For now we see through a glass, darkly; but then face to face: now I know in part; but then shall I know even as also I am known[1].


In Chapter Eleven of the novel, the novel's central character, Bob Arctor / Fred, thinks to himself:

What does a scanner see? I mean, really see? Into the head? Down into the heart? Does a passive infrared scanner … see into me — into us — clearly or darkly? I hope it does see clearly, because I can't any longer these days see into myself. I see only murk. Murk outside; murk inside. I hope, for everyone's sake, the scanners do better. Because if the scanner sees only darkly, the way I myself do, then we are cursed, cursed again and like we have been continually, and we'll wind up dead this way, knowing very little and getting that little fragment wrong too.

The protagonist is both Bob Arctor, member of a household of drop-out drug-users, and Agent Fred, an undercover police agent assigned to spy on them. Arctor/Fred shields his true identity both from those in the drug subculture and, ironically, from the police themselves. The requirement that narcotics agents remain anonymous, to avoid collusion and other forms of corruption, becomes a critical plot point late in the book. While supposedly only posing as a drug user, Arctor becomes addicted to Substance D (also known as Slow Death, Death or D), a powerful psychoactive drug. An ongoing conflict is Arctor's love for Donna, a drug dealer through whom he intends to identify high-level dealers of Substance D. Arctor's persistent use of the drug, which causes the two hemispheres of the brain to function independently, produces the strange scenario in which Arctor and Agent Fred do not realize they are the same person. Incapable of combining what each persona knows, Fred begins spying on himself, Arctor, more passionately. Through a series of drug and psychological tests, Arctor's superiors at work discover that his addiction has made him incapable of performing his job as a narcotics agent. Donna takes Arctor to "New-Path", a rehabilitation clinic, just as Arctor begins to experience the symptoms of Substance D withdrawal. It is revealed that Donna has been a narcotics agent all along, working as part of a police operation to infiltrate New-Path and determine its funding source. Unknowingly, Arctor has been selected to penetrate the secretive organization.

The flow of the book is consistent and author's knowledge and experience of drug culture creates a feeling of realism.
I didn't put it down till I finished it . . .
A must read.