By far the best thing about this mystery debut is lawyer Wheat's crisp evocation of the world of Legal Aid law in Brooklyn--especially the black-comedy and pathos of night court. Her heroine is Legal Aid attorney Cass Jameson, whose older lover/ colleague Nathan Wasserstein is found murdered in his apartment--apparently in the midst of an S/M homosexual liaison. Cass can't believe that Nathan had this secret sex-life. Moreover, she suspects that the murder is really connected with a client of Nathan's--a crook who turned informer against the Mob. . . and who himself promptly turns up dead, a supposed jail-cell suicide. Meanwhile, however, another of Nathan's clients--a teenage hustler--is arrested, and Cass winds up as his defense lawyer, doubly determined to prove the surly kid's innocence. And, after yet a third death (the prosecutor who was obsessed with nailing the Mob network that sabotaged all his cases), Cass ends up as the prisoner/victim of the evil, nicely surprising non-Mob villain. Some corny moments, especially at the end, and some implausible plotting--but an above-average first mystery overall, made distinctive by Wheat's no-nonsense savvy in writing about the shabby details and scruffy denizens of the Legal Aid/ night-court world.