Perhaps the most chilling reveal is Mary’s response to the truth. After finding proof of Theresa’s darkness in a buried box of love letters from Kit, Mary chooses to protect her daughter’s memory by doubling down on her lies. She holds a press conference blaming Emma for the killings and exposes Emma’s new identity to the world, essentially painting a target on her back while knowing she is innocent.
The series’ biggest "truth bomb" lands when Emma confronts Mary with the reality of her missing daughter. It turns out wasn't a victim of Kit Parker—she was his partner. Theresa had a violent streak and was actually the one who killed Amy Walker. Emma reveals that before she met Kit, he and Theresa were already acting out murders together. Mary’s Descent Tell Me Your Secrets 1x10
To top it off, Mary executes Theresa’s former swim coach, who had molested her years ago, proving that she has fully embraced her own role as a "monster". Perhaps the most chilling reveal is Mary’s response
