Ending a five-year hiatus after his bestselling debut (The Fourth Procedure), Pottinger proves he is a master of the art of the medical thriller and a formidable voice in examining American race relations. Here, he examines racial tensions in a plot that includes a vast web of biotechnical dangers and political corruption. New York police detective Nat Hennessy is coerced by his boss to exploit the trust of his fianc e, architectural restorer Camilla Dissonette, the beautiful granddaughter of an aristocratic New Orleans family. It's part of a conspiracy to discredit Dr. Cush Walker, a brilliant and controversial African-American neurosurgeon short-listed for a Nobel in medicine. Walker, who also happens to be Dissonette's ex-boyfriend, invented a breakthrough brain-scanning technique for detecting the predisposition for racial bias. This advanced polygraph-type analysis, called the BIAS test, threatens the careers of many cops, including Hennessy. Other effects of Walker's work involve the development of technology to restore damaged brains and transplant personalities, used in the hopes of eradicating the legacy of racial bigotry. Peopled with quixotic characters who enrich the mosaic of revenge, murder and intrigue, the action bounces around like machine-gun fire in a dark alley, while Pottinger makes pseudo-technobabble somehow sound simple. Though one must forgive the occasional clich d lapse in the romantic scenes and minor side trips to smell the roses (and garbage), this kaleidoscopic thriller is marvelously complex, charged with emotional impact and resounding ethical questions. (Feb.) FYI: Pottinger served in civil rights positions in both the Department of Justice and the former Department of Health, Education and Welfare.