Leto glided along behind her, reviewing the breeding programme, shaping the necessary decisions for a replacement should she fail.

As the night progressed, Siona moved slower and slower. First Moon was high overhead and Second Moon well above the horizon before she stopped to rest and eat.

Leto was glad of the pause. Friction had set up a worm-dominance, the air around him full of the chemical exhalations from his temperature adjustments. The thing he thought of as his oxygen supercharger vented steadily, making him intensely aware of the protein factories and amino acid resources his worm-self had acquired to accommodate the placental relationship with his human cells. Desert quickened the movement toward his final metamorphosis.

Siona had stopped near the crest of a star dune. “Is it true that you eat the sand?” she asked as he came up to her.

“It’s true.”

She stared all around the moon-frosted horizon. “Why didn’t we bring a signal device?”

“I wanted you to learn about possessions.”

She turned toward him. He sensed her breath close to his face. She was losing too much moisture into the dry air. Still she did not remember Moneo’s admonition. It would be a bitter lesson, no doubt of that.

“I don’t understand you at all,” she said.

“Yet, you are committed to doing just that.”

“Am I?”

“How else can you give me something of value in exchange for what I give you?”

“What do you give me?” All of the bitterness was there and a hint of the spice from her dried food.

“I give you this opportunity to be alone with me, to share with me, and you spend this time without concern. You waste it.”

“What about possessions?” she demanded.

He heard fatigue in her voice, the water message beginning to scream within her.

“They were magnificently alive in the old days, those Fremen,” he said. “And their eye for beauty was limited to that which was useful. I never met a greedy Fremen.”

“What’s that supposed to mean?”

“In the old days, everything you took into the desert was a necessity and that was all you took. Your life is no longer free of possessions, Siona, or you would not have asked about a signal device.”

“Why isn’t a signal device necessary?”

“It would teach you nothing.”

He moved out around her along the track indicated by the Pointers. “Come. Let us use this night to our profit.”

She came hurrying up to walk beside his cowled face. “What happens if I don’t learn your damned lesson?”

“You’ll probably die,” he said.

That silenced her for a time. She trudged along beside him with only an occasional sideward glance, ignoring the worm-body, concentrating on the visible remnants of his humanity. After a time, she said: “The Fish Speakers told me that you ordered the mating from which I was born.”

“That’s true.”

“They say you keep records and that you order these Atreides matings for your own purposes.”

“That also is true.”