10 Subtle Ways Movies Foreshadowed Major Spoilers
5. Joan's Newly Bought Chalkboard Confirms She's A Fraud - Hereditary
Ari Aster's masterful horror film Hereditary ends with the reveal that the majority of the film's events have been orchestrated by a coven to destroy the Graham family and weaken young Peter (Alex Wolff) enough that he can become the vessel for the demon-king Paimon.
The ending also reveals that Joan (Ann Dowd), an apparently bereaved woman who Peter's mother Annie (Toni Collette) had become friends with, was part of the coven and manipulating Annie all along.
Memorably, it's Joan who suggests that Annie conduct a seance to communicate with her dead daughter Charlie (Milly Shapiro), under the guise that she herself had made contact with her own dead son and grandson.
Joan demonstrates this apparent ability to Annie by seemingly making contact with her departed family members on an heirloom chalkboard, but if you pay close attention during the earlier scene where Joan first mentions the seance to Annie, we can see a brand new chalkboard in her car.
This makes it clear that Joan and Paimon concocted the ruse to trick Annie, and yet, it's so ingeniously hidden in plain sight that, in the moment, you'd never give it a second thought.