First, as you know, the cult has the belief that the only way to create peace after trauma is through death, there’s no other release from trauma.
We see the main dude see that David, the new boyfriend, puts the red lantern up outside when the main character was in that room watching the laptop video.
Then the stuff with the wine and violence/death happens right after.
What you saw when they were looking out at the hills at the end, there were specks of ‘other’ red lanterns being lit or already lit all across Los Angeles hills.
So the characters realize the lantern is a signpost, that confirm coordinated murder parties are happening and their own is not a singular incident. Basically a mass, coordinated cult terrorist attack.
You even hear the characters at the end say “call the police, call an ambulance”, then based on all the lanterns the reality falls on them that it’s gonna be mass chaos and help would be spread too thin around the city.
I can see how this could be missed though if you hadn’t seen all the lanterns when they were looking out at the hills right before it cuts to credits.
It’s just a twist ending, and I think the “is-our-main-character crazy paranoid or not” theme throughout the movie was super entertaining to try to figure out.
Logan Marshall-Green, he seems like he’s all the way into every part I see him in.
