The Dungeon Master

From the Front Flap:

When James Dallas Egbert III disappeared from the Michigan State University campus in 1979, he was no ordinary college dropout. Egbert was a computer genius at sixteen, a boy with an I.Q. of 180-plus and an extravagant imagination. He was a fanatic Dungeons & Dragons player - before the game was widely known - and he and his friends played a live version in a weird labyrinth of tunnels and rooms beneath the university. These secret passages even ran within the walls of buildings themselves. After Egbert disappeared, there were rumors of witch cults, drug rings, and homosexuality to try to explain the mystery.