Unlike quiet predators who try to disappear, Rader demanded to be seen. He mailed letters to newspapers. He sent cryptic puzzles. He bragged about murders the public didn’t even know about yet. He signed his crimes with a name designed to shock. BTK wasn’t just committing murder. He was building a brand.

It was late in the afternoon of Sunday, December 10, 2023, when 81-year-old Sharron Hilda Schwartz put a plate of hot pancakes on the...