"Therese Raquin," Masterpiece Theatre's latest offering, is everything a true devotee of soap opera longs for -- three hours packed with lust and torment, dastardly crimes, treachery, agony and wonderful acting. The first hour begins at 9 p.m. tomorrow on Channel 26.

Based on Emile Zola's first important novel, published when he was 27, "Therese Raquin" is set in Paris in 1875. Its main characters are a wimpy clerk, his bubbling, burbling mother, his wife Therese, and his old friend Laurent.

Therese is afflicted with nearterminal boredom, caught in a bourgeois routine defined by her domineering, endlessly cheerful mother-in-law and her sickly husband. Her boredom, which has reduced her to a zombielike state, may have something to do with the fact that her husband is also her cousin, and she has shared his bed since she was 6 years old. She is a woman who's "got out of the habit of doing anything real."

Their monotonous lives, a ritual composed of Raquin's daily return from the office -- his mother's fabric store -- and a weekly evening of tea and dominoes with a few friends, is enriched by the addition of Laurent, a handsome erstwhile painter and part-time bounder. Soon he and the torpid Therese have locked eyes, then lips, and then are pursuing each other with a relentless passion reminiscent of athletes in competition. The two lovers are reduced to a kind of sniveling desperation in which being together is the only thing that matters to either of them. (Warning to parents of young children: these scenes are very sexy, and there is some nudity.)

Since divorce is out of the question, murder is in. Without giving away too much of the plot, by the end of the first episode Camille Raquin, Therese's husband, is dispatched. As the story proceeds, the lovers find they have killed their passion along with Raquin, deranged by fear of being discovered, guilt and the hollowness of a love based on deceit and amorality.

Their fate is symbolized in a series of particularly gruesome scenes of Laurent's daily visits to the city morgue in hopes of finding Camille Raquin's body. Naked bodies in varying stages of decay are displayed on marble slabs in a courtyard, on view to the public, including giggling children. The (perhaps too) lengthy scenes of Laurent pursuing his grisly task set the tone for the rest of the series, as the lovers -- lovers no more -- torture each other into doomed madness.

They reach their nadir when Raquin's aging mother has a stroke and is rendered speechless. They taunt her by revealing their previously hidden crimes and passions, their illicit love affair, the murder and their now uncontrollable loathing for each other, while she, hearing all, is unable to react. They become so miserable that each decides to kill the other, but instead -- well, those who haven't read the novel should thrash through the agonies to discover the ending for themselves.

Fortunately the actors are able to revel in this melodrama. As the weakly Camille, Kenneth Cranham has a voice that sounds like a cat whose tail has been stepped on, and Brian Cox as Laurent reveals the subtle layers of a man going from eager lust to evil to dumb, burtalizing guilt.

But the women are particularly wonderful. Dear old Mona Washburn allows the plump, chattering mother to be endearing where she might just have been an annoying old bat, and communicates through expression alone her mute agony as the two lovers parade the dirty secrets that destroy all her illusions. She seems almost to lose her innocence, an old lady whose wrinkled face changes from ignorant gentleness to disillusionment and fear.

Kate Nelligan zips into the role of Therese, a role that enchanted great stage actresses two generations ago, with abandon. Her languor is so deep that it is almost rude; a rebuff to everything and everyone in general. Her lust is equally consuming, insatiable and totally reckless. Thus her tradually deepening madness is consistent; her ability to hide her true emotions from the conventional friends and family that surround her is pathological, and her fate seems inevitable.