Deep Red
In 1975, Dario Argento directed this famous film. This classic case of whodunit comes with a lot of romantic tension between a local Roman musician (David Hemmings) and an investigative journalist (Dario Nicoldi). This movie is scary in a way that it will make you reconsider how you've thought about the minds of artists. True sickness remains hidden.
M
That's right, this one is just called M. When a serial killer sets his sights exclusively on hunting children, an unnamed city begins to implode. It takes a village, or in this case, an entire secret gang of criminals, to take this villain to justice. Though you might have never seen it, this film set the precedent for all serial killer movies. That, and this movie still holds up nearly 100 years after its conception