"The Two Jakes," Jack Nicholson's long-awaited sequel to "Chinatown," is about ghosts. It's a movie about remorse and loss and the plagues of memory that is itself haunted by the past.

This is true both in ways that the filmmakers intended, and in ways they couldn't have. Following in the footsteps of a film as popular and acclaimed as "Chinatown" is a loaded proposition to begin with; if history is any guide, comparisons are almost certain to be unfavorable. Nicholson himself has said that if the picture is half as good as the original, then he could view his efforts as a success. Unfortunately, it's not -- not by half. Not by a lot more than half.

The dominant feeling of "The Two Jakes" is one of nostalgia. The cruelly nihilistic ending of Roman Polanski's original film left an indelible tragic footprint, and for the film's characters -- particularly Nicholson's private eye hero, Jake Gittes -- the 11 years since then have been prosperous but not recuperative. The past is still alive in Gittes; it still torments and ensnarls him. "I don't want to live in the past," he says. "I just don't want to lose it."

He doesn't seem to have much choice, though, and neither do we. The past is still alive in us as well; we have our own ghosts, our own captivating nostalgia. And what "The Two Jakes" makes us long for most is the earlier film, for Faye Dunaway and John Huston, for the old "Chinatown," the old Jack Nicholson.

"The Two Jakes," which Nicholson directed from Robert Towne's screenplay -- a script that reportedly was significantly rewritten -- is a scrambled mess, impenetrably and ineptly plotted, and a failure on its most basic levels, as a detective story and as an elaboration of its themes.

The themes are there, but mostly as shadows; they're ghosts too. "The Two Jakes" is more a reaction to "Chinatown" than a sequel. Its setting is 1948, and Nicholson has designed the narrative so that the events of the two films reverberate off each other, both for us and for the characters.

The film's springboard is a murder, and initially the connections between it and the events of the earlier film are unclear. Jake Berman (Harvey Keitel), a real estate developer and the movie's second Jake, walks in on his wife, Kitty (Meg Tilly), during a motel rendezvous with her lover -- who, it just so happens, is her husband's business partner -- and shoots him dead.

Since Berman was Gittes' client and aware of his wife's infidelity, the interruption was planned and well documented, with both a tape recording and photographs. The murder, however, was not, and Gittes' job throughout most of the film is to discover his client's motives and unravel the layers of intrigue and double-dealing surrounding the crime -- and to keep himself from being either killed or thrown into jail.

It's possible to lay out the further intricacies of the film's plot -- just as it's possible to explain the solutions to the Rubik's Cube -- but, well, another time perhaps. One detail is essential, though, especially to Gittes. While playing back the tape recording of the conversation between Kitty and her lover before Berman charges in, Gittes hears a reference to Katherine Mulwray, the incestuous offspring of Noah Cross and his daughter, Evelyn Mulwray, in the previous film. The tape is scratchy and the meaning of the reference even more obscure, but the detective's protective instincts are activated and he sets out to find the girl.

All of this -- the murder, the relationships, the motives of the characters -- is laid out with an overwhelmingly casual fuzziness. In the first film Polanski gave Towne's narrative a terse propulsiveness and urgency, but Nicholson's style is strolling and discursive. There's no fire in his direction.

Because actors are more interested in behavior than in plot, what the films they direct lack in narrative drive is made up for in the quality of the performances. Sadly, though, "The Two Jakes" is without these compensations. The real disappointment is Nicholson's performance. As the divorce rate has increased and the city has grown more prosperous, so has Gittes. A respected figure in the community, he owns his own building, belongs to a country club and is engaged to be married -- he's a member of the Establishment now. In the first film the insubordinate street brawler was never completely disguised by the polished manners and expensive tailoring. Here, with his figure padded out from rich living, he's more like a languorous pasha than the pugnacious smart aleck of the previous film.

The volatile, hipster edge is gone from Gittes, but it's gone from Nicholson as well. Early on, he appears to want to play the character as a doofus, and the performance is so sleepy-eyed that it almost seems as if he is playing his scenes for comedy. Later, he appears to rouse himself, and the performance at least begins to have some logic, but still, Nicholson's emotions seem embedded, fatty. When he's called upon to deliver the goods -- such as a scene in which he flips through his file on the Mulwray case and sorts through his old regrets -- his acting seems hollow, disengaged. You don't buy it.

It's impossible not to find something appealing about a Nicholson performance. His wears Wayne Finkelman drapy fashions with style (the big-lapelled jackets somewhat disguise his girth), and he smokes more evocatively than any actor since Bogart. But engaging as it is, this is star glamour and not acting.

The work he does with the other actors is uneventful, too, mostly because their characters are too schematic and unresolved. Nicholson worked magnificently with Keitel in "The Border" (Nicholson's most underrated and, perhaps, last great performance), but though there's a kind of comradely feeling between them here, their scenes lack dynamism -- something that seemed unimaginable with Keitel.

As Lillian Bodine, the wife of Berman's murdered partner, Madeleine Stowe is broad and unappealingly hysterical; though she has a few moments of low comedy, she seems miscast, wasted. As Kitty Berman, Meg Tilly is the opposite -- seductively ephemeral -- but her character is so shrouded in mystery that we can't make sense of it.

But we can't make much sense of anything -- even though, late in the project, a narration was added to help us, with hard-boiled lines that seem more a parody of the genre than an evocation of it -- and after a point, we give up trying. On a deep level, "The Two Jakes" is a tone poem about the transformation of Los Angeles and the devastation of the city's postwar boom. Towne's script for "Chinatown" was the first of a planned trilogy of films about Los Angeles, and it combined the conventions of the detective story with elements of the historical essay. In that sense too, this film -- with its concentration on the exploitation of the oil reserves beneath the city -- elaborates on the lessons of the first, which dealt with water. But the scenes that might develop these ideas are missing. As a result, all we're left with are vestiges and pale suggestions. And memories.

The Two Jakes, at area theaters, is rated R and contains some adult material.