“Vatican III” (season 1, episode 7)

Three plots in this one: first, assessors arrive from the Vatican to figure out if Grace, who’s now back in China, was a false prophet or a true one; they give Kristen, David, and Ben access to the original codex, which has gaps in it that Grace’s drawings were helping to fill. The trio realizes the occult symbols it contains—some of which they recognize, including one drawn by Leland in a diary he gave to Kristen’s daughters—represent the sigils of different demons lurking on Earth, also known as “the 60.”
Elsewhere, the investigators meet a woman who claims to be possessed by a demon and may be a serial child killer. It’s unnerving, but the most stomach-turning storyline sees Leland start mentoring a budding misogynist named Sebastian. He nudges him toward becoming a dangerous incel—introducing him to like-minded haters on 8chan, and shaming him into taking violent action—and the arc continues until episode nine, “Exorcism Part 2,” when an increasingly militant Sebastian accidentally shoots himself with one of his new firearms… much to Leland’s disgust.