For exactly two-thirds of its 97 minute running time, "Cruel Intentions" scores as a nasty-minded, wryly satiric and even mildly courageous teen update of "Dangerous Liaisons." But, like so many movies with one eye cocked towards the boxoffice, "Cruel Intentions" loses its nerve and settles ultimately for comfortable, safe and hopelessly dull conventionality. Ryan Phillippe and Sarah Michelle Gellar portray a wicked pair of step siblings who operate together to prey sexually upon unsuspecting victims, manipulating others to achieve their goals of personal conquest and revenge. It's refreshing to encounter protagonists who make no excuses for their amorality and instead allow themselves to be completely guided by their own self-serving impulses, totally unmindful of the consequences to others. Their schemes are acted out with a callous gleefulness and self-absorbed relish that raises the film to a level of surprisingly sophisticated satire and audacity. But, when Sebastian encounters his ultimate challenge - a midwestern virgin played by Reese Witherspoon, who has publicly declared in a magazine her decision to wait for true love before offering herself to a man - he falls under her charms and suddenly transforms from coldhearted predator to mushheaded romantic. This is the major problem with the film. Sebastian is valid and interesting as a character as long as he stays within the realm of sly manipulator and acerbic scoundrel. When he is called upon to function as a dashing romantic figure, he loses both credibility and uniqueness - and the film itself goes into a freefall tailspin. For, as Sebastian undergoes his sudden conversion, all the sharply satiric wit simply drains out of the film. We're ultimately left with little more than unconvincing melodrama, inappropriately tragic overtures and a silly evildoers-do-not-prosper resolution. What a pity to see yet another in a long line of movies that start out with bright promise, but which finally end up renaging on their initial courageousness, leaving the audience in perpetual frustration.