Coherence (2013) - [Synopsis: Strange things begin to happen when a group of friends gather for a dinner party on an evening when a comet is passing overhead.]
Hearing breaking glass, the group heads outside to find someone smashed the window on Hugh's car. The non-verbal communication happens when...
spoiler
they separate to check their own cars for any damage. When Kevin comes to check on Em at her car, there is this moment where they both go completely silent. No one speaks but it's clear that Em realizes she's not talking to her Kevin, but one of the variants. At the same time, it's clear the alternate Kevin realizes he's not talking to his Em either, but a version of her that's a stranger to him (and us, the audience).
They're surrounded in the complete darkness of the night in the power outage blackout of the neighborhood, the only lighting in the entire scene are the flashlights they have pointed at each other's faces. Without a word, they slowly back away from each other, light fixed on each other's faces, slowly disappearing in the darkness opposite of each other to escape, each one scared of the other.
It's so delightfully unnerving and creepy, one of the most effective scenes out there. If you haven't seen it, the movie is included with Amazon Prime Video if you have that. If you like unraveling mysteries or mind-bending movies, don't read anything else about the movie and go watch it spoiler free!