Norman Leith was a radical architect who was depressed and suicidal until his disappearance in 1983 (2 months after the disappearance of Max Shea). Considering his character, the disappearance came not as a surprise, but New Frontiersman connected it with Shea's and other creative figures around the same time.
Apparently he was taken to the Veidt's island to work on a secret project with the other vanished people. Months later a Pyramid Deliveries ship came to take them and Max Shea noted that even he was smiling. He was killed when the ship exploded, leaving nobody alive to talk about it.