Jack Nicholson has taken a big risk with "The Two Jakes," not just because he's created a sequel to "Chinatown," one of the best-regarded films of the '70s, and not just because he has directed it, following in the footsteps of Roman Polanski at his peak.

"The Two Jakes" is a risk mainly because it's so unlike any other movie playing this summer and because it is much more a specific extension of the first film's story than any other sequel in years. Also because — let's be honest here — a generation or two has grown up since "Chinatown" and never seen the film.

In fact, even if you have seen "Chinatown," I suggest you rent it again before seeing "The Two Jakes." The latter refers so specifically to the original that if you've forgotten about the character of Katharine Mulwray, you may find yourself lost when "The Two Jakes" reaches its apex about two-thirds in.

Nicholson has tried to make the complex script of "Two Jakes" more understandable by adding a voiceover narration, which is at once sharp-tongued and annoyingly wordy and cumbersome. An homage to Raymond Chandler's Los Angeles is OK, but this is sometimes more a self-conscious copy.

The setting is 1948 Los Angeles, 11 years after "Chinatown," and J.J. Gittes (Nicholson) is a fat cat — successful, a member of a posh country club, engaged to be married, a war hero and at peace with the past. Or is he?

The film opens with a blurry image that is eventually revealed, by the soundtrack, to be a couple making love. As the scene goes into focus we see the image is merely the reflection in a camera lens. Gittes is still doing marital investigations.

The scene that follows is similar to the opening scene in "Chinatown," with Gittes apparently revealing to a client that his wife has been unfaithful. But there is a phoniness to the client's speech. Gradually we see that it's because he's learning a line of dialogue to speak when Gittes helps him burst in on his unfaithful wife and her lover.

This telling scene also reveals that the client is named Jake Berman (Harvey Keitel), a coincidence since Gittes is known as Jake to his friends.

The shocker comes in the next scene, however, as Berman breaks in on his wife (Meg Tilly) and her lover — and Berman shoots the lover dead.

Where'd Berman get the gun? Why did he do it?

Things get all the more suspicious when Gittes discovers that Berman and the victim were business partners — and now Berman gets the entire business to himself.

Was it a setup? Was Berman's wife in on it?