Apparently inspired by a recent case in New York's Soho neighborhood, this body-blow of a novel zeroes in on the agony of a mother whose child is missing: she's 34-year-old Susan Selky, a divorced teacher of college English, and one May morning her six-year-old son Alex walks off to his Boston school. . . and disappears from the face of the earth. At first: ""Susan felt herself sink into a well of horror so great that it was all colors, all light and all darkness, scalding heat and killing cold. . . ."" And then, with nerveless exactitude, Gutcheon monitors the numb drifts and burning center of a woman trapped in pain. What seem to be lifelines of help--from intimates and strangers, police and media--fall short, as leads and neighborhood involvement dissolve over the months. Boston police--led by raggedly empathic Detective Al Menetti, a blunt and baggy-eyed pro--set up a battle station in Susan's house, bring in extra telephones, fan out for neighborhood interrogations. The media, Susan's hope for reaching any witnesses, arrive in an aggression of flashbulbs and mikes. Friends rush in, most of them helplessly pitying and frightened--like ex-husband Graham. Eventually, however, Susan's ""pain beyond sense"" hardens to commitment, to a faith that Alex is alive; by this ""act of will"" she perseveres in her determination to keep the face of little Alex before a now-apathetic public--even as the ""Missing"" posters are fraying, the neighborhood committee is becoming lethargic, and the media are losing interest. And finally--after compounding cruelties (false accusations against Susan's homosexual friend, Graham's mugging by a trickster) add to Susan's new, sinister view of the world--Alex will be found. . . but emotionally damaged, perhaps, beyond repair. Powerful material--and, with Gutcheon (The New Girls, 1979) tuning the tension to such a shattering pitch, this gut-appeal story, so heartbreakingly familiar, shapes up like a cinema-bound, commercial winner all the way.