It's a 1950s big bug movie, but it's also classy and directed by Jack Arnold.

The plot's simple enough. One day a zombie mutant freak from Michael Jackson's Thriller video dies in the desert. This is surprising in a movie called "Tarantula". John Agar is a small-town doctor who's invited to take a look at the body and doesn't understand what he's seeing, which is reasonable enough. He assumes that this guy must have been suffering from a hideous long-term disease, but then Leo G. Carroll walks in and says it's a friend of his and that the cause of death was acromegalia. (They mean "acromegaly", i.e. the bone-deforming growth condition of Rondo Hatton, Richard Kiel and possibly Abraham Lincoln.) Furthermore, four days ago the guy was fine. He looked normal. Agar points out that you don't catch "acromegalia" and then die of it in the space of four days, but Carroll isn't budging from his story.

The secret of course is that Carroll is experimenting with growth nutrients. He has rats the size of children and guinea pigs the size of pigs. He also has a... well, you can guess.

Firstly, the production. Jack Arnold is probably the best-regarded director of this genre and era, with films including Creature from the Black Lagoon, Revenge of the Creature and The Incredible Shrinking Man. An Arnold film is likely to be more intelligent than its peers and have nearly flawless special effects that are impressive even today, in the CGI era. It looks real. Here he avoids puppets and models, instead using real creatures, matt work and a miniature desert landscape. It helps of course that as usual he's working in black-and-white, which makes everything look classier and more convincing, but even so this is thoroughly professional work and a pleasure to look at.

Secondly, the casting. There's something slightly wrong about it, in a manner so interesting that it almost becomes subtext. Carroll's playing the mad scientist, except that both the script and the casting undercut this. We're talking about Leo G. Carroll. He's lovely. He's not without misjudgements, but he's a good, caring man who's working for the future of the human race. Here's some of his dialogue. "The disease of hunger, like most diseases, well, it spreads. There are 2 billion people in the world today. In 1975 there'll be 3 billion. In the year 2000, there'll be 3,625,000,000. The world may not be able to produce enough food to feed all these people. Now perhaps you'll understand what an inexpensive nutrient will mean." It's charming irony that the world's actual population in 2000 was twice that.

John Agar though has a slightly villainous air. To me, he seems smug. This is curious because here he's playing the all-American hero, yet even so he was giving me a whiff of The Brain From Planet Arous.

So the hero's wrong. The mad scientist's wrong. The girl's wrong, since she's played by the gorgeous Mara Corday and yet her name's Steve. (I'm a Corday fan, but this is a straightforward role and she's straightforward in it.) Clint Eastwood's wrong, being one of the all-time greats of the movie industry and yet only getting an uncredited appearance of a few seconds. (He and Corday would be lifelong friends, so did they first meet on this film?) All these off-kilter things add colour to the obvious wrongness of a spider that hides behind mountains and can smash trucks.

The science is surprisingly non-risible, instead giving you the impression that these medical men and professors know what they're talking about. However this is only a first impression, helped by the film's honest attempt at avoiding 1950s-isms. However there are still a few:

1. "Synthesis is impossible without a bonding agent to hold everything together." "And we use the simplest of all... the atom!" Darn those atoms. We'd better ban them.

2. On finding a pond of spider venom near some flesh-stripped skeletons, you should taste it.

3. If you have a nutrient that can cause uncontrollable growth and have fatal side-effects, do you really want even the slightest traces of it in human food? Admittedly Carroll and his colleague have been wanting to conduct human tests, except that the way they're going about it suggests that their goal is to make super-sized people. Maybe their anti-famine plans involve cannibalism?

4. This hundred-ton tarantula can walk around, instead of crushing itself to death as its weight is cubed while its muscular strength is squared. (Tarantulas are actually surprisingly fragile.)

However that last point is unfair, since this is after all a Big Bug movie. Furthermore, despite these hiccups, the film convinces. Its portrayal of the work and risks involved in creating growth nutrient is a good representation of the scientific process, while I admire the way they've chosen to use acromegaly as a side-effect. It's detailed, plausible and accurate. Note also the lecture from a naturalist, accompanied by well-chosen film footage, in which we learn real-life facts about tarantulas that are scarier than anything fictional.

As a big bug movie, it's refreshing. It's mostly a movie about scientists and the ways in which their work triumphs or goes wrong, keeping the tarantula largely offscreen until Act Three. Incidentally some critics have lamented the fact that it's so quickly defeated at the end. Not me. I was turning cartwheels. I get bored to tears by films that degenerate into thirty tedious minutes of "the U.S. military vs. the giant rampaging monster", yet here Jack Arnold gallops through all that in under ten minutes. It's pacy, it works and it could almost be called exciting (for once).

On top of that, though, I also liked the film's characterisation of this sleepy desert town and its inhabitants. There's the nosy but lovable old coot who works as the phone operator and listens in on people's conversations. There's a pushy journalist. There's an elderly sheriff who doesn't beat about the bush. I particularly enjoyed the conversation in which Corday learns that it would be fruitless to call a cab, because that would be Jim and he won't be back for a couple of hours. The film takes an endearing interest in these people, but it's also contemplative about the desert itself. "Serene, quiet, yet strangely evil, as though it were hiding its secret from man." "You can't end guess the desert. Rocks that have stayed for a thousand years just move. There's no figuring."

If you watch 1950s SF for its kitsch value, you're out of luck. This is a good film. It's solid, intelligent and covering all the bases. Yes, it got name-checked by Rocky Horror, but I think all the films mentioned in "Science Fiction/Double Feature" are well respected.