Whose loss is it anyway? That's the bone of contention between a gay man and a straight woman who meet to straighten up loose ends following the death of the man they both loved. Harvey Fierstein's one-act, part of his Safe Sex trilogy, is a short, sometimes fiercely funny, and finally poignant study of how the universal situation of losing a loved one takes on unique new qualities in the context of AIDS. The dead man's ex-wife, Marion, wrestles with unresolved conflicts stemming from the breakup of her marriage. Not sure of her own feelings and insecure about her own health, she must also guide their nine-year-old son through the trauma and stigma of his gay dad's death. And Arthur, the lover who nursed the dead man through a two-year battle for life, struggles with resentment at being the odd man out in the aftermath of his lover's death--overlooked in obituaries, ignored by family, stuck with leftover bills, and avoided by his embarrassed and hostile surrogate stepson. Fierstein, who has an exceptional gift for capturing the roller-coaster emotions of people faced with such circumstances, probes and pokes at the unique pain and heroism AIDS brings out in those touched by it, and the script's grim quips and anxious outbursts are sensitvely handled in this special engagement, mounted as a benefit for Season of Concern, the theater community's AIDS-support fund-raising project. Christine Hunter is moving as the wrought-up ex-wife--she seems to visibly grow young, then age, as she mentally travels back to her college courtship and up to her present bereavement. Andrew Leman is in fine Fiersteinian form as the lover--cuddly and caustic, a compulsive caretaker transformed by grief and resentment into a raw bundle of exposed nerve endings. Halsted Theatre Centre, 2700 N. Halsted, 348-0110. Monday, September 21, 7:30 and 9 PM. $7.50 in advance; $10 at the door.