This movie does a good job of doing exactly what it wants to do. "Jurassic Park III" is not as awe-inspiring as the first film or as elaborate as the second, but in its own B-movie way it's a nice little thrill machine. One of its charms is its length--less than 90 minutes, if you don't count the end credits. Like the second half of a double bill in the 1940s, it doesn't overstay its welcome.

One of the ways it saves time is by stunningly perfunctory character development. There's hardly a line of dialog that doesn't directly serve the plot in one way or another. Even Sam Neill's pontifications about those who would trifle with the mystery of life are in the movie only as punctuation, to separate the action scenes. In a summer when B-movie ideas like have been blown up to gargantuan size and length with A-movie budgets, here is an action picture we actually wish was a little longer.

Part of its brevity is explained by the abrupt ending, which comes with little preparation and will have you racing to the dictionary to look up (ital) deus ex machina. (unital) Trained by the interior tides and rhythms of most action movies, we're blindsided by the ending, which comes when we expect the false crisis, followed by the false dawn, and then the real crisis and the real dawn. We can't believe the movie is really over, and when some flying Pteranodons appear, we expect another action scene, but no--they're just flapping their way overseas to set up the next sequel.

The movie begins with a 14-year old named Eric (Trevor Morgan) parasailing with his mother's boyfriend over the forbidden island of Isla Sorna, off the coast of Costa Rica. You will recall that this is the location of the doomed theme park in "The Lost World: Jurassic Park II."

The tow boat disappears into a mist of fog and emerges sans crew, and the parasailers crash on the island. Cut to America, where the boy's divorced parents (William H. Macy and Tea Leoni) offer a big bucks donation to the research of famous paleontologist Alan Grant (Sam Neill) if he will be their guide for a flight over the island.

Grant thinks they are tourists; their secret is that they plan to land the plane on the island and rescue him. Along for the ride are Neill's gung-ho assistant (Alessandro Nivola) and three other crew members, some of whom are quickly eaten by dinosaurs, although for a change the black character doesn't die first. The search for Eric consists mostly of the survivors walking through the forest shouting "Eric!" but the movie is ingenious in devising ways for prehistoric beasts to attack. There are some truly effective action sequences--one involving flying lizards and a suspension bridge, another involving an emergency rescue with the recycled parasail--that are as good as these things get.

I also liked the humor that's jimmied into the crevices of the plot. There are two nice gags involving the ringer on a cell phone, and a priceless exchange of dialog between the 14-year-old and the expert paleontologist:

Dr. Grant: "This is T-Rex pee? How'd you get it?"

Eric: "You don't want to know."

I am aware that "Jurassic Park III" is shorter, cheaper and with fewer pretensions than its predecessors, and yet there was nothing I disliked about it, and a lot of admire in its lean, efficient story telling. I can't praise it for its art, but I must not neglect its craft, and on that basis I recommend it.

Footnote: That last shot obviously means that the giant flying Pteranodons are headed to civilization for "Jurassic Park IV." I am reminded of the 1982 movie "Q," in which a flying reptile monster builds its nest atop the Chrysler Building ands flies down to snack on stockbrokers. The movie was screened at Cannes, after which its proud producer, Samuel Z. Arkoff, hosted a gathering for film critics, at which I overheard the following conversation:

Rex Reed: "Sam! I just saw your picture! What a surprise! All that dreck--and right in the middle of it, a great Method performance by Michael Moriarity!"

Arkoff: "The dreck was my idea."