Soapbox oratory masquerading as a mystery. Crammed between polemical pauses: Who strangled Loie Marsh--a noted anti-porn activist--with a dog collar (classic S&M symbol) during a Seattle conference on women and sexuality? Para Nilsen (Murder in the Collective; Sisters of the Road; not reviewed) seeks the truth while coming to terms with a souring love affair, and with her twin sister having a baby. Among the suspects: an aggressively S&M duo; a feminist erotic filmmaker; a brilliant student doubling in a live sex show (she's soon dog-collared to death, too); a Bible-thumping ex-husband; and his neoconservative present wife. Endless speeches and sermons later, Pam finds an old porn movie--starring the strangled women, an embarrassed fellow, and the killer, who struck in order to keep the film hidden. Weak as fiction, with the story a mere prop to hang feminist/lesbian violence and pornography theory on.