Cassie (Sandra Bullock) is a hyper-serious police detective. As an ex-boyfriend once tried to kill her and, indeed, left her grievously wounded, she is determined to bring those who harm others to justice. As the result of her near-death experience, also, Cassie favors one-night stands and trusts no one. One day, a woman is found dead in the woods near Cassie's community. She has been murdered heinously, beaten severely and left to die alone. Naturally, Cassie will stop at nothing to find the murderers. Assigned to help her is fellow officer, Sam (Ben Chaplin). He soon discovers Cassie's relentless attitude and all-consuming instincts when she asks him to pick up a sample of vomit that has been left at the scene for analysis, among other actions. The trail soon leads them to two high school students, Richard (Ryan Gosling) and Justin (Michael Pitt). Could these teenagers really be responsible for the planning and execution of the perfect "joy" killing? This is an intriguing film, but viewers should be warned that the subject matter is grim indeed. Killing for the "sport" of it is seldom the topic of films that are of the "all sweetness and light" variety and this one is no different. That said, the cast is great. Bullock, without a hint of her talent for comedy, is terrific as the police officer whose own past compels her to lock up the evil folks of the world. Chaplin, too, is quite nice as the detective who is both attracted and repelled by the forceful Cassie. As for Gosling, he gives a most memorable performance as a brilliant mind with a satanic soul. The production values for the movie are good, too, with appropriately fine costumes, settings and photography. If you are a fan of Bullock's looking for a laugh, this is not the one for you. But, if you adore mysteries, even those with the grimmest of plots, you will find this tale enthralling.