Chinatown (the slapping scene):

The scene where Jake continuously slaps Mrs. Mulwray in the face is an unexpected conflict that contributes a great deal to Chinatown’s overall narrative arc by revealing new and hidden qualities of the characters and of the story itself while significantly advancing the plot.

Slapping Mrs. Mulwray shows Jake’s growing frustration. He came across as such a cool, collected, calculated and even reasonable guy up to this point but he was tired of getting the run around and certainly lost his cool completely. There was no other time in the film that he lost it like this (the scene in the barbershop gave a glimpse into the possibility of it but even then he managed to pull it together).  On one hand, it shows a very personal attachment he must have had to Mrs. Mulwray since that level of frustration can only come from a deeper connection. On another hand, it shows that he’s capable of hitting a woman, that he has limits and that he’s not perfect, and it reveals he’s willing to go to the extreme to get to the truth.

For Mrs. Mulwray, it showed her at her weakest. She came across as so strong and pulled together prior to this moment where she completely breaks and her secret flies out into the open. She seems utterly exhausted, too, as though she’s been working so hard to keep her secrets hidden for so long and to keep her stories straight in her own head. In addition, it showed a deeper quality we hadn’t seen before—the quality of an abused woman. By not standing up for herself in this scene and just letting this man slap her like that, it was clear that she had the unfortunate mentality of a person who had lived a life of abuse and may have even grown to believe she deserved it. 

Both characters reach their breaking points in this scene. Also, they start to show qualities that seem opposite to the characters we were introduced to at the start of the film. But this is another thing that makes the story so great. The characters are clearly multidimensional. It’s not that they suddenly changed personalities here, but rather it showed that they have inner demons which they worked hard to hide from the world in addition to having weaknesses and the ability to change and grow through stress and circumstance.

Breaking the characters like this advances the plot in several ways. The obvious one is that now Mrs. Mulwray’s secret is out in the open and something must happen next because of it. But also, it shakes the viewer up and potentially alters our perspective. For example, seeing Jake get physical with Mrs. Mulwray caused me to question him as a man and reconsider his likeability. I think that’s a natural reaction to watching a man slap a woman in the face like that. It also made me feel sorry for Mrs. Mulwray in an uncomfortable way because it was clear to me that she had deeper rooted issues than had been revealed.  But most dynamically, this scene changed the game. If you weren’t awake or already paying close enough attention up till now, you certainly woke up and started focusing. It was almost like Jake slapped Mrs. Mulwray, himself and the viewer in the face all at once.

I believe this scene was one of the most dramatic and successful scenes in the movie. Personally I didn’t expect it. While it caught me off guard in the moment, in retrospect it really worked. It shook me up but then everything about the narrative and the characters started coming together and the entire story started making sense.