While possibly a minor homage to The Strangers, the home invader who follows Mary around for a solid 10-15 minutes of the film invokes a sense of sheer, unadulterated paranoia that you are being watched, which Mary is clearly feeling. She was right.
The Polite Stranger. Easily the most psychotic character in the film, even more than Grace and the neighbours while maintaining an Affably Evil vibe for the ENTIRE MOVIE.
The news reports of the Purge at the end. One reporter says the streets are covered with bodies. Another man says he saw people walk into an apartment, drag everyone out, and then summarily execute them all in the street.
Mary, having seen her husband die and now being tied up along with her children to be killed, goes from begging for their lives, to resigning herself that they will all die and begging to be able to hold her children one more time before their deaths.
Despite their good intentions to protect their children, James and Mary tying up the stranger and aggravating his wounds and deliberately torturing him into submission is very hard to watch, especially with poor Charlie and Zoey having no choice but to watch their parents descend to savagery. The Stranger's muffled screams of agony are a mix of horrifying and sad.
Honestly, the fact that James and Mary (James more so) expect this poor man to die for their sake makes it even worse. The fact that these privileged and wealthy individuals are okay with sending someone less fortunate to their death is also scary in it's own right.
The Stranger's situation in general is a complete nightmare and the whole movie may very well be an even bigger Trauma Conga Line for him more than the Sandins. To put it lightly, he goes through nothing but hell the entire movie, even when he seemingly catches a break from one kid's act of kindness, it's still dangerous for him given that the deranged Purgers after him are still very intent on killing him despite the shelter he managed to find thanks to Charlie.
Adding to that, despite the horror that all the main characters go through, the Sandins at least have each other to protect, the Stranger has nobody looking out for him, aside from the youngest child Charlie, who could only do so much to protect him.
The Purger's exaggerated classist views to the point where they constantly dehumanize The Stranger is also quite scary. Narm aside, it's quite terrifying to see how sadistic some entitled and wealthy people can be.
