cassie ( sandra bullock ) be a hyper serious police detective . a an ex boyfriend once try to kill her and and indeed and leave her grievously wound and she be determine to bring those who harm others to justice . a the result of her near death experience and also and cassie favor one night stand and trust no one . one day and a woman be find dead in the wood near cassie community . she have be murder heinously and beat severely and leave to die alone . naturally and cassie will stop at nothing to find the murderer . assign to help her be fellow officer and sam ( ben chaplin ) . he soon discover cassie relentless attitude and all consuming instinct when she ask him to pick up a sample of vomit that have be leave at the scene for analysis and among other action . the trail soon lead them to two high school student and richard ( ryan gosling ) and justin ( michael pitt ) . could these teenager really be responsible for the planning and execution of the perfect joy kill . this be an intriguing film and but viewer should be warn that the subject matter be grim indeed . kill for the sport of it be seldom the topic of film that be of the all sweetness and light variety and this one be no different . that say and the cast be great . bullock and without a hint of her talent for comedy and be terrific a the police officer whose own past compels her to lock up the evil folk of the world . chaplin and too and be quite nice a the detective who be both attracted and repel by the forceful cassie . a for gosling and he give a most memorable performance a a brilliant mind with a satanic soul . the production value for the movie be good and too and with appropriately fine costume and setting and photography . if you be a fan of bullock look for a laugh and this be not the one for you . but and if you adore mystery and even those with the grimmest of plot and you will find this tale enthralling .