He spent the afternoon and the next day wandering, sitting on flat rocks and watching the little rivulets bounce downstream. Once he remembered how fast water had fallen on Earth. Unnatural. No. But this was his place, known and loved, every dyad and every clump of campion, even the speed of water as it lofted off stone and plashed down in its smooth silver shapes. The way moss felt under the finger pads. His visitors were people for whom Mars was forever an idea, a nascent state, a political situation. They lived in the tents and they might as well have been in a city anywhere, and their devotion, while real, was given to some cause or idea, some Mars of the mind. Which was fine. But for Nirgal now it was the land that mattered, the places where water arrived just so, trickling over the billion-year-old rock onto pads of new moss. Leave politics to the young, he had done his part. He didn’t want to do anymore. Or at least he wanted to wait until Jackie was gone. Power was like Hiroko, after all— it always slipped away. Didn’t it? Meanwhile, the cirque like an open hand.

• • •

But then one morning when he went out for a dawn walk, there was something different. The sky was clear, its purest morning purple, but a juniper’s needles had a yellowish tinge to them, and so did the moss, and the potato leaves on their mounds.

He plucked the yellowest samples of needles and sprigs and leaves, and took them back to the workbench in his greenhouse. Two hours’ work with microscope and AI did not find any problem, and he went back out and pulled up some root samples, and bagged some more needles and leaves and blades and flowers. Much of the grass had a wilted look, though it wasn’t a hot day.

Heart thudding, stomach taut, he worked all day and into the night. He could discover nothing. No insects, no pathogens. But the potato leaves in particular looked yellow. That night he called Sax and explained the situation. By coincidence Sax was visiting the university in Sabishii, and he drove up the next morning in a little rover, the latest from Spencer’s co-op.

“Nice,” Sax said as he got out and looked around. He checked Nirgal’s samples in the greenhouse. “Hmm,” he said. “I wonder.”

He had brought some instruments in his car, and they lugged them into the boulder and he went to work. At the end of a long day he said, “I can’t find anything. We’ll have to take some samples down to Sabishii.”

“You can’t find anything?”

“No pathogen. No bacteria, no virus.” He shrugged. “Let’s take several potatoes.”

They went out and dug potatoes from the field. Some of them were gnarled, elongated, cracked. “What is it?” Nirgal exclaimed.

Sax was frowning a little. “Looks like spindle tuber disease.”

“What causes it?”