Film: Two into one will go - spookily

TWINS: CINEMA has always been drawn to these exclusive, visually confounding creatures. The affair continues this week with The Parent Trap, a Nineties update of the gooey 1961 Hayley Mills vehicle. But don't be put off: such offerings belong to the anodyne wing of a wonderfully off-beat obsession.

Twins (particularly identical ones) are a shorthand, a means to explore identity, whether in the material world (The Prince and the Pauper plot) or deep within the soul (the good vs evil dynamic). Life-swapping is the dream twins can make real and the line "You don't seem quite yourself today" is a bedrock of the movies. Twins, in other words, embody our crooked confusions - beautiful but freakish. Look at how few twins are actually used in films: it's the concept we like, not the reality.

The best directors turn such conventions inside out. In Tod Browning's Freaks, for example), Siamese twins Daisy and Violet Hilton play themselves. Violet is all charismatic defiance, Daisy intelligently gentle, and the bond between them is so wittily drawn, so intimate and complex, that any notion of them as tragic or repulsive becomes absurd. Violet protects her sister from a bullying husband; Daisy sits with her eyes rapturously closed as her sister is kissed. It's envy that the sisters inspire - those of us without a body attached to our sides, those of us who can't share our life, are left feeling incomplete, bereft.

Of course, as Freud's shadow fell across Hollywood, things got more complicated. With scriptwriters obsessed by ids, egos, schizophrenia and narcissism, twins became the perfect way to explore the divided self. And for actresses to get twice as much of themselves up on screen (narcissistic. Who them?) The result? Lots of female stars battling against psychosis, in films such as The Dark Mirror, with Olivia de Havilland, and A Stolen Life (1946), starring Bette Davis.

Davis obviously enjoyed herself - she played twins again in 1964's Dead Ringer. Twins Maggie and Edith - Maggie the scheming bitch, Edie the bitter saint - suddenly find themselves, after years apart, in Maggie's palatial bedroom. Mirrors, as so often in such movies, provide the clues. When Edie's flashing, paranoid orbs are drawn towards the looking glass, you know she's a moral goner. What follows is ludicrously OTT. Jealous Edie demands Maggie come to her greasy apartment, where she shoots her. With a gothic harpsichord giberring in the background, Edie drags the tights from Maggie's dead legs, then fiercely combs water through her back-combed hair. It's worthy of a French and Saunders skit, yet powerful. The doomed, insecure desire to adopt another's personality sends shivers down all our spines. And what a great moment of recognition for Bette's draggy, corpse-robbing fans.

By the Seventies and Eighties, the psychological mists had all but evaporated. Instead, we get semi-pornographic flicks: Twins of Evil, Twinsanity...Thankfully, David Cronenberg's 1988 classic Dead Ringers re-introduced the mystery, providing Jeremy Irons with his best role(s). Like Freaks and even Dead Ringer, Dead Ringers transforms our sense of the "unnatural". The story of two brothers, Bev and Ellie, joined at the brain, it is most un-American (try imagining a John Wayne cowboy movie in which an identical twin shows up). The fact that the boys have girls' names is also significant.

In one of the film's best moments, Bev (the weaker twin) is lying in bed with Claire (Genevieve Bujold) - the first person to make him want to separate from arrogant Ellie. He has a dream in which he and Ellie are joined by an umbilical cord - an ugly, ragged bit of flesh which Claire, in order to release him, begins to chew. We're swept along by Bev's relaxed limbs and milky smile. Then comes the nightmare jolt - it can't be done, she's eating him. Psychologists would class such fears as pre-Oedipal. Here, that's the only state we're in and Cronenberg's tenderness towards his characters makes the resultinghorror even more unbearable.

Twins continue to fascinate us, but with diminishing returns (see Jean- Claude VanDamme's Double Impact). Should we despair? Dead Ringers was based on a true story and there are plenty more out there. A number of aging identical twins have plastic surgery to maintain their "identical" looks.

It's not re-makes of The Parent Trap we need. How about Dead Ringers II - Under the Surgeon's Knife?