Then there was an odd scene that I certainly missed on my previous readings of this book. Duncan awakens from a dream in which he saw a scroll listing weapons and details of their construction. He then goes to his workroom, sits at his console, and the scroll returns but this time with different weapons, including Futars and weapons he had never heard of such as Disruptors. Then suddenly, he sees the elderly couple he has seen through the shimmering net before and they glare at him and say "Stop spying on us!" (Chapterhouse: Dune, p. 335)
So somehow, Duncan can see through to the elderly couple ... they, with Duncan, are the key to the climax of the entire Dune Saga. Here is his analysis of this vision:
Resonances and tachyon theory held his attention for a time. Tachyon theory figured in Holzmann's original design. "Techys," Holzmann had called his energy source.
A wave system that ignored light speed's limits. Light speed obviously did not limit foldspace ships. Techys?
"It works because it works," Idaho muttered. "Faith. Like any other religion."
Mentats squirreled away much seemingly inconsequential data. He had a storehouse marked "Techys" and proceeded to go through it without satisfaction.
Not even Guild Navigators professed knowledge of how they guided foldspace ships. Ixian scientists made machines to duplicate Navigator abilities but still could not define what they did.
"Holzmann's formulae can be trusted."
No one claimed to understand Holzmann. They merely used his formulae because they worked. It was the "ether" of space travel. You folded space. One instant you were here and the next instant you were countless parsecs distant.
Someone "out there" has found another way to use Holzmann's theories! It was a full Mentat Projection. He knew its accuracy from the new questions it produced.
(Chapterhouse: Dune, p. 335 - 336)