"Back to the Future, Part II" may be the first feature-length segue.

This isn't really a movie at all — it could never stand on its own. Rather it seems to be simply a means of getting to "Part III" (which will open next summer; scenes from "Part III" close "Part II").

"Back to the Future, Part II" begins exactly where the first film left off, with wild-eyed Doc Brown (the ever hilarious Christopher Lloyd) telling Marty McFly (Michael J. Fox) and his girlfriend Jennifer (Elizabeth Shue, replacing Claudia Wells) that they need to go with him into the future to see what happens to their kids.

The future they enter is a wild place — justice happens in minutes because all lawyers have been abolished, the Cubs win the World Series and Marty puts on shoes that automatically snap and a jacket that adjusts itself.

At the local theater is "Jaws 19" (directed by Max Spielberg, Steven Spielberg's son) with a holograph that scares Marty to death, though he walks away muttering, "The shark still looks fake." A nice in-joke, and there are many.

Then when Marty hops aboard a skateboard "hovercraft" for a zany futuristic reprise of the famous chase scene from the first film, it works as both self-spoofery and imaginative invention.

This sense of joyful adventure is maintained as we see Marty's future home, with his 40-plus future self, his son and daughter (both also played by Fox) along with dozens of bizarre, humorous futuristic touches (all photographed with incredible special effects that allow one actor to play two or three characters in a scene with a roving camera, and not a hint of fakery).

But then Marty and Doc Brown are forced to return again to 1955 (by virtue of a plot device far too complex to try and explain here, though it initially resembles "Time After Time") and many of the first film's scenes are replayed showing a new viewpoint. When this occurs the film becomes overly convoluted and the humor seems displaced by the sheer momentum of the movie itself, which, by the way, is the most chaotic, headache-inducing collection of images to play a movie theater in some time.

Lea Thompson as Fox's mother is back, but Crispin Glover as his father is glimpsed only in long shots from the first film, and much more screen time is given Biff (Thomas F. Wilson), which only proves that a little of his character goes a long way.

By the way, if you haven't seen the first film — or even if it's just been awhile — you may get lost along the way. Imagine a TV miniseries is playing three nights in a row and the only episode you see is the middle one. You'd feel a bit left out, right?

That's how it is with this film, which is OK I suppose, since "Back to the Future" is in the all-time top 10 list and the filmmakers no doubt assume those who go will have seen the first film.

That was the assumption with "The Empire Strikes Back," so why shouldn't it also work in this case? But "The Empire Strikes Back" retained the heart, spirit and sense of wonder that "Star Wars" began. "Back to the Future, Part II" has the spirit, but it lacks the heart of the original film, and more importantly, much of the humor.

I watched the first film again before seeing the sequel, so I got the jokes that made reference to the first film, but I laughed a lot more and a lot harder watching the original film on video for the third time than I did watching "Part II" for the first time in a theater full of moviegoers.

Still, there are some incrediblethings here, and for that first third or so, as mentioned, an amazing sense of wonder builds as we see a most unique inside-out view of the future (though some of the jokes — particularly the '80s Club sequence, seem to owe something to Woody Allen's "Sleeper"). Too bad that couldn't have been maintained for the length of the film.

"Back to the Future, Part II" is rated PG for violence, profanity, a few vulgarities and some glimpses of nude photos in a "girlie" magazine.