CUPPI"" stands for ""Circumstances Undetermined Pending Police Investigation""--which is what the cagey N.Y, Police Dept. often calls a murder when it doesn't seem likely to be solved. And the CUPPI here is the death of a twelve-year-old girl fallen or pushed from a hotel window in Manhattan's midtown porn district. The police would be happy to write the case off, but divorced, violence-obsessed photographer Homer Wood is determined to investigate--apparently because the dead girl looks like his own daughter. He manages to track down the dead girl's equally prepubescent companion, mulatto waif Winter, and their story emerges in a clumsily inserted flashback: the girls were runaways from two stereotypical sorts of unloving homes, and, after some good times as freelance child-prostitutes, they got fatally involved with some brutal pimps. Homer is eventually aided by the cops--and by his new love, a half-Indian feminist psychiatric intern--and when they all close in on the child-porn villains, a decoy is needed; so Homer snappily enlists his chirpy twelve-year-old daughter (a move that the reader is apparently supposed to applaud). And meanwhile Winter has disappeared, only to turn up at the end as a confirmed, hardened prostitute: ""Wood felt his heart splinter into a million ragged pieces. . . ."" We're told that this ""was inspired by an actual case,"" but--except for a few atmospheric details and snatches of gritty cop dialogue--it's indistinguishable from a dozen similar TV-movie scenarios, with weak characterizations and the usual blend of sentiment and sleaze.