By Walter Mosley. Little, Brown. 306 pp. $24.95

It is a matter of legend that Walter Mosley's career took off one fine day in 1992 when Bill Clinton named him as one of his favorite novelists. Mosley fits squarely within the tradition of African American authors writing about race and blackness and has been compared to Ralph Ellison (Invisible Man). In an interview with the New York Times recently, Mosley said: "I have never met an African American who was surprised by the attack on the World Trade Center. Blacks do not see America as the great liberator of the world. Blacks understand how the rest of the world sees us, because we have also been the victims of American imperialism."

Given all that, one would expect a Mosley novel based in the Los Angeles suburb of Watts at the height of the devastating race riots of 1965 to amount to more than a simple murder investigation, and Little Scarlet does not disappoint. Although the story is narrated in the first person by Easy Rawlins, who is the hero of a series of Mosley novels, the true protagonist of the book is collectively the riots and their aftermath. Mosley is considerably more interested in the ambiguous state of mind of the black citizenry, the disorientation of the cops and the looted, shambolic condition of Watts itself than he is in the adventures of his hero. Watts, in truth, is a world turned upside down, and Mosley simply points his hero at it and rolls the camera.

The vehicle Mosley has chosen by way of plot is neatly ironic and perfectly mirrors the social inversion of the times: A black woman, Nola Payne (the Little Scarlet of the title -- she has red hair), has been brutally murdered. Fingers are pointed, inevitably, at a white man who was seen with her in Watts during her last hours. But in the high fever of boiling racial tension, the last thing the white cops need is a white perpetrator. On the other hand, failure to investigate would also be seen as highly provocative by the black community. Escalation must be avoided at all costs. Only a child of the streets, a black man with no direct affiliation to white authority, a humble 45-year-old with enough civic responsibility and integrity to be interested in keeping the uneasy peace that followed the riots -- a big, comfortable, family man blessed with quiet charm who can take care of himself in a punch-up and talk back to white cops who do not appreciate his mission and have a lot to hide when it comes to the identity of the true killer -- only Easy, in other words, can possibly save this day that rests on a knife edge. But our hero, with the help of the young and voluptuous Juanda, quickly establishes that the white man didn't do it. The more he digs, the more the evidence points to a quite different kind of villain. So where in L.A. is the culprit? How many black women has he killed already? Why did he kill them? Why haven't the cops investigated him in the past and -- above all -- what color is he? In the end, naturally, the perpetrator is identified thanks to Easy, who almost single-handedly defuses this social time bomb.

To flesh out his hero, Mosley endows him with imposing height, great physical strength, enormous skill in street pugilism and an occasional associate, the killer Raymond "Mouse" Alexander. ("Telling him no was was as dangerous a task as moving nitroglycerine in a truck with no shock absorbers." ) In evoking the atmosphere of Watts after the riots, Mosley is nothing less than masterly: "All he had left was the burnt and broken worktable surrounded by a couple hundred pairs of scorched shoes. Why would somebody want to burn shoes?"

Mosley is also fearless in exploring the underlying ambiguity of race: Negro National Guardsmen bully blacks in perfect imitation of their white colleagues; it is an out-of-town white cop, Detective Melvin Suggs, who bends the rules in order to send Easy off on his mission; some African Americans are so brainwashed by white elitism they will go to insane lengths to present themselves as Caucasian; poor whites without a racist bone in their bodies are left financially ruined by the riots.

The only quibble I have with Little Scarlet, which I enjoyed immensely, concerns the character of the hero. It is commonplace that the lone male who, in the guise of detective or other secret agent, goes about righting wrongs and fighting for the virtue and dignity of women, is a direct descendant of the Arthurian knight, and Easy is a product of this noble line. He never refuses a joust, he gets embroiled with at least one adversary so big, mean, muscular and bad that he can fairly be called a monster, his anger is always of the righteous kind within his chivalric code and he manages to resist the lascivious temptation presented by Juanda.

So far so good, but it is in the nature of narrative that great heroes must have great weaknesses if they are to avoid the genre of fairy tale. Philip Marlowe knew himself to be compromised by the Los Angeles of the '40s, drank heavily and lost as many fights as he won; Holmes loved cocaine; Bond was a relentless womanizer; Lancelot was a passionate adulterer and traitor to his king -- and Quixote was mad. Rawlins, by contrast, is pretty much flawless. Perhaps Mosley wants to show us that a black knight is even better than a white knight, which would explain why dear old Easy hardly misses an opportunity to spell out his virtues ("That's why she liked me, I stood up for myself but still didn't lord it over other people when I had the upper hand") and can come across as somewhat anachronistic in his political correctness.

Personally, I found myself wishing that our hero possessed more in the way of breadth and depth. As I understand it, Watts was part of a mighty revolution that changed America and perhaps the world. I would have liked Rawlins to experience more directly for us the sheer psychological rawness of that time, which Mosley prefers to elicit from third parties: the catharsis following the sudden release of centuries of pent-up rage, the thrill and fear of anarchy, the gnawing terror of the rough beast now unleashed, the squalor and shame of the looting of blacks by blacks, the pride of the African American community that was finally fighting back. Certainly, Easy has plenty of very reasonable, even anodyne, opinions about race and riots; not a lot of convincing gut reaction, however. He is just a tad too good to be true. That aside, Little Scarlet is a terrific yarn from a tormented moment in recent American history. *

John Burdett has published a number of novels, the most recent being "Bangkok 8."