The Knife (1961)

Original title: Het mes

A boy is resentful of his mother's budding romance with the best friend of her late husband, and is torn and confused about his emerging feelings for Toni, a young girl in his neighborhood. His fascination with an antique Oriental knife leads him to steal it and he uses it to try to impress Toni while at the same time trying to break up his mother's relationhip.