Weird dynamics arise when married couple Andrzej (Niemczyk) and Krystyna (Umecka) impulsively invite a young male hitchhiker (Malanowicz) on a boating excursion. The boy accepts, and at first it's smooth sailing. Tensions gradually escalate as Andrzej sees the younger man becoming a bit too attentive towards his wife. The plot thickens from there. Will all three make it back to shore alive?

Here, a young and unknown Polanski crafted a psychological thriller of the first order, and was catapulted to international fame virtually overnight. It's all devilishly subtle: while overt action is fairly contained, the viewer senses turmoil roiling beneath the surface of things, and waits breathlessly for the inevitable breaking point. Nominated for Best Foreign Film at the Oscars, this "Knife" is as sharp as they come.