Film: Also showing - The vegetarian's guide to the galaxy

Star Trek: Insurrection (PG) The Acid House (18)

Star Trek: Insurrection is the ninth in the series of films born from the 1960s television show. This time, the crew of the Starship Enterprise saving a group of comely vegetarians living on a planet whose atmosphere sustains eternal youth. It looks like Switzerland. All the crew of the old Enterprise were retired in 1991 after William Shatner (Captain Kirk) saw the rushes and insisted on his bottom being airbrushed. (In space, nobody must see you sag.) Shatner was replaced by the British actor Patrick Stewart, who does stints at the RSC between films and is quite stern. His character, Captain Jean Luc Picard, is a bit like Inspector Morse in that he knows his Proust from his Paganini and is always falling for truculent women.

Stewart has a stretched, precise kind of face, perfect for a film quite mad about physiognomy. Insurrection has its very own culture of confusing implants passing for aliens. Here a fin, there a flipper, everywhere leopard- skin warts and bendy blemishes and cobweb veins. The baddies are more scurrilous than fiendish, and secretly want to get home to Mum. Whenever there's a gap in the plot, everybody starts talking about "postatrionic matrixes" and "warp drives". The crew are obsessed with who has the greatest warp capability, and eyes fill at the suggestion that there might be a superior one in the offing. There are a few gentle special effects, moments of amused condescension, the odd creative idea, but essentially Insurrection never stops being familiarly jolly and antiquated.

All the Star Trek films are old-fashioned - very much how the past saw tomorrow. They are really about intergalactic etiquette and striving to be decent. Nothing rude happens, ever. You suspect the men are wearing girdles under their Lycra. Insurrection does display a preoccupation with metaphysics and cloning, but there are no computer-as-God horrors, none of the night-sweat theatrics characteristic of good science fiction. Instead, the film simply asks how many people have to suffer before their suffering is recognised as a calamity.

The Acid House is a triptych of short films adapted for the screen by Irvine Welsh from his collection of short stories. Because no story connects to another, the overall film is episodic and sketchy. In the first film someone is turned into a fly after meeting God in a bar; in the second, a boy is manipulated by his loutish girlfriend and revolting neighbour, and in the last (and most substantial) an acid-popping teenager swaps his brain for a new born baby's. It's bleak and empty humour; uncomplex Kafka. Welsh's Acid House was published in 1994, the year after Trainspotting. Both books, set largely in poverty-row Edinburgh and written in grumpy slang, offer an insider's point of view, not a journalist's. In both, the men rage and the women are physical, not emotional. Little conventional kind of psychology is offered, and yet Welsh still manages to put us right at the centre of his characters' consciousness - his people might be gormless, but never stupid. Director Patrick McGuigan's film struggles with this challenge, this deviousness. There's even a clumsiness with the language, the very thing that gives Welsh's work excitement and violence. But in the film, all the "blootering" and "swedging" and "gouching" feels self-conscious and learnt.

The film is very corporeal. Like David Cronenberg, McGuigan likes sooty fingers, congealed sauces, blackheads. But where the book secretly aches, the film feels like a collection of clever bad jokes. Welsh offers half- parables, but the film doesn't dare.