Antiretroviral drugs, used to treat people infected with HIV, are now widely available in South Africa. This wasn’t always the case, and the period before this was so forms the backdrop for Masande Ntshanga’s disquieting novel “The Reactive.” At the center of the book is Lindanathi, a young man who, along with two of his friends, engages in a number of morally gray activities, including selling antiretroviral drugs to residents of Cape Town.

It’s a life on the fringes of society, and Lindanathi has many of the ingredients of a classic existential hero: a sense of detachment — “it’s still a long stretch of time before I die,” he says early in the book — along with a fluctuating bond with those closest to him and an event in his personal history that serves as a catalyst for his life going forward.

Ntshanga doesn’t leave any ambiguity about the nature of that event. “The Reactive” opens with a bold first sentence: “Ten years ago, I helped a handful of men take my little brother’s life.” What follows is a haunting description of those events, and their influence on Lindanathi’s current circumstances is made clear.

Over the course of the novel, Ntshanga reveals glimpses of Lindanathi’s past that occurred between the killing and the present day, including a brief span when he held a promising job. All of this leads to a number of questions pertaining to how Lindanathi went from there to the much bleaker circumstances in which the reader finds him. Tension accelerates when Lindanathi and his friends enter the presence of an ominously scarred man looking to make a substantial drug purchase.

Even as “The Reactive” hits some story beats that readers of a certain melancholy strain of crime fiction will find familiar, it also evades them. This is as much a book about atmosphere and states of mind as it is about the activities in which Lindanathi is enmeshed. And fundamentally, it’s not so much about the dangers that Lindanathi encounters on a daily level.

Instead, it’s about answering the question of how he came to be in this position, and how his guilt has slowly spread itself across all aspects of his life. This is an affecting, slow-burning novel that gives a fantastic sense of a particular place and time, and of the haunted inner life of its protagonist.

 Tobias Carroll is the managing editor of Vol. 1 Brooklyn.

The Reactive
By: Masande Ntshanga.
Publisher: Two Dollar Radio, 161 pages, $15.99.