M (1931)

A child killer prowls the streets of Berlin. The public want him caught as soon as possible. The police want to be the ones to catch him. And the criminal underworld wants him gone by any means.
A large part of filmmaking is intuitive, but even so, any director worth their salt in the past 80+ years has been influenced by Lang’s expressive techniques. M was his first sound film and he used it like he used everything else: expertly. It enabled him to have things happen off-screen and to imply menace when otherwise there would appear to be none.
Peter Lorre is perfectly cast. If you've ever doubted his acting abilities, M will put an end to them. The last act is unforgettable stuff.

4½ lost balloons out of 5