Gately, the wraith, and the figurants — "had seen his own personal youngest…"
had seen his own personal youngest offspring, a son, the one most like him, the one most marvelous and frightening to him, becoming a figurant, toward the end. […] No horror on earth or elsewhere could equal watching your own offspring open his mouth and have nothing come out. The wraith says it mars the memory of the end of his animate life, this son’s retreat to the periphery of life’s frame.
Context
The theory's real referent: Hal (unnamed — "his own personal youngest offspring, a son") diagnosed in pure cinematography, "becoming a figurant," retreating "to the periphery of life’s frame" — mouth moving, no sound out, exactly the 'Cheers!' background-patron spec. The family "looked but did not see his invisibility"; seeing-without-seeing is the film-optics failure the whole apparatus of the man's late career answers. The passage retro-fits the book's opening scene (Hal audible to himself, inaudible to the room) as the figurant condition fully arrived (that link is a reading, not the raw's claim).