In the summer of 1979, the New York Times reported that a 16-year-old student at Michigan State University named James Dallas Egbert III had gone missing while playing a “bizarre intellectual game.” In his dorm room, campus police had discovered a suicide note as well as a corkboard covered in thumbtacks that seemed to map out the school’s underground steam tunnels. From the boy’s mother, police learned that Dallas had recently developed an interest in a game in...