His back was turned and he did not see that sudden stiffening of her shoulders, or the sudden eagerness that seized her fingers as they adjusted the focus. But he did feel the wave of emotion that welled from her, impinging directly on his empathetic sense. “What is it?” he called to her, as if she had spoken aloud.

“Something … something here,” she said, “in this leucocyte. It’s not normal structure, but it’s familiar. I’ve seen something like it before, but I just can’t remember.” She turned away from the microscope and unthinkingly pressed her gory knuckles to her forehead. “I know I’ve seen it before.”

Brion squinted into the deserted microscope and made out a dim shape in the center of the field. It stood out sharply when he focused—the white, jellyfish shape of a single-celled leucocyte. To his untrained eye there was nothing unusual about it. He couldn’t know what was strange, when he had no idea of what was normal.

“Do you see those spherical green shapes grouped together?” Lea asked. Before Brion could answer she gasped, “I remember now!” Her fatigue was forgotten in her excitement. “Icerya purchasi, that was the name, something like that. It’s a coccid, a little scale insect. It had those same shapes collected together within its individual cells.”

“What do they mean? What is the connection with Dis?”

“I don’t know,” she said; “it’s just that they look so similar. And I never saw anything like this in a human cell before. In the coccids, the green particles grow into a kind of yeast that lives within the insect. Not a parasite, but a real symbiote….”

Her eyes opened wide as she caught the significance of her own words. A symbiote—and Dis was the world where symbiosis and parasitism had become more advanced and complex than on any other planet. Lea’s thoughts spun around this fact and chewed at the fringes of the logic. Brion could sense her concentration and absorption. He did nothing to break the mood. Her hands were clenched, her eyes staring unseeingly at the wall as her mind raced.

Brion and Ulv were quiet, watching her, waiting for her conclusions. The pieces were falling into shape at last.

Lea opened her clenched hands and smoothed them on her sodden skirt. She blinked and turned to Brion. “Is there a tool box here?” she asked.

Her words were so unexpected that Brion could not answer for a moment. Before he could say anything she spoke again.

“Not hand tools; that would take too long. Could you find anything like a power saw? That would be ideal.” She turned back to the microscope, and he didn’t try to question her. Ulv was still looking at the body of the magter and had understood nothing of what they had said.