When reading the synopsis of the Knife in the Water, one thinks this will be a standard suspense/thriller where the hitchhiker terrorizes the unsuspecting couple. Instead we get a psychological battle of wills that builds sexual, class, and generational tensions in a non-contrived and realistic fashion. Not much is said and the hidden feelings of the characters are only implied for most of the film, but it is as captivating a piece of cinema as you will ever find. Polanski made other great films that he is better known for, but this might be his greatest achievement. It is a one of kind masterpiece.