Was the young screenwriter Kevin Williamson picked on by the most popular kids in school? That's my theory after seeing the two films that he has written, both of which catalogue the many fun ways in which teenagers who think they are cool can be terrorised and/ or mutilated on their way to the grave. Williamson must hate these kids; he puts them through hell. The audience doesn't get off lightly, either. Although I Know What You Did Last Summer has none of the wit or ingenuity of Williamson's first film, Scream, it is an efficient slasher movie which delivers its shocks straight from the conveyor belt, though knowing what's coming doesn't let you off being terrified.

The film takes its title from an anonymous note delivered to the house of Julie (Jennifer Love Hewitt) when she returns to her home town for the summer break. So what did she do last summer? Oh, you know, the usual teenage stuff. Drinking. Making out. Being involved in a hit-and-run accident after which she and three friends dumped their half-dead victim in the ocean. Now it appears that either someone witnessed their unsavoury exploits, or the unfortunate fellow has risen from his watery grave and is out for revenge.

There's no denying that the picture is a real mess - unlike Scream, it doesn't have the governing hand of a horror master like Wes Craven to steer it towards the finishing line. A director who thinks it's acceptable to cut from a heart-stopping chase to a scene of a girl doing computer research in her bedroom has no business being placed in charge of a horror film, but despite the misjudgements in Jim Gillespie's direction, the movie retains an appealing grubbiness that can make you squirm. And you can tell by the games that Williamson plays that he really relishes the chance to splash around in the slasher genre.

All the old favourites are here. "He's in the closet!" "He's in the car!" At one point, a character even screams, "He's behind you!" When the climactic revelation comes, it smacks of Scooby Doo, but by that time you may be too jittery to care.

Ronan Bennett is another screenwriter who has had modest success this year and is about to have his second feature released, though he couldn't be more different from Williamson. In his new film, A Further Gesture, Bennett explores characters who are trying to reconcile political ideals with their personal lives. Dowd (Stephen Rea) is an IRA prisoner who breaks out of jail and hotfoots it to New York. Once there, he starts washing dishes to pay for a pitiful existence in a run-down hotel, before falling in with a group of Guatemalans who are planning a daring assassination on a former torturer.

Like the gangster hero of Bennett's thriller, Face, Dowd is wrestling with inner demons which drive him further into a violent life even as his conscience makes him recoil, and Stephen Rea's stoney exterior only makes the character seem more explosive. The director, Robert Dornhelm, handles the opening escape sequence with aplomb, and though there's a staginess to the later scenes which smothers much of the tension, this is still a mature and compelling work.

My expectations of Persons Unknown were high, given that it was directed by George Hickenlooper, who made the haunting civil war ghost story The Killing Box, and Hearts of Darkness, which documented the making of Apocalypse Now. But this B movie-style thriller about the security expert (Joe Mantegna) who becomes intrigued by a roller skater (Kelly Lynch) and her disabled sister (Naomi Watts) is all over the place. The dynamics of the relationship between the siblings are intermittently fascinating, and Mantegna is always good value for money, as is JT Walsh, as a corrupt cop with a passion for stun guns. But the slapdash climax only confirms your suspicions that Hickenlooper has directed the film with a blindfold on.

All films open today