Davout strove to keep the impatience from his voice. "Lessons are learned from failures as well as successes. Experience is gained, life’s knowledge is applied to subsequent occurrence. If we deny the uses of experience, what is there to make us human?"

His sib was patient. "Sometimes the experiences are negative, and so are the lessons. Would you have a person live forever under the shadow of great guilt, say for a foolish mistake that resulted in injury or death to someone else; or would you have them live with the consequences of damage inflicted by a sociopath, or an abusive family member? Traumas like these can cripple the whole being. Why should the damage not be repaired?"

Davout smiled thinly. "You can’t tell me that these techniques are used only in cases of deep trauma," he said. "You can’t tell me that people aren’t using these techniques for reasons that might be deemed trivial. Editing out a foolish remark made at a party, or eliminating a bad vacation or an argument with the spouse."

Silent Davout returned his smile. "I would not insult your intelligence by suggesting these things do not happen."

Q.E.D. Davout signed. "So how do such people mature? Change? Grow in wisdom?"

"They cannot edit out everything. There is sufficient friction and conflict in the course of ordinary life to provide everyone with their allotted portion of wisdom. Nowadays our lives are very, very long, and we have a long time to learn, however slowly. And after all," he said, smiling, "the average person’s capacity for wisdom has never been so large as all that! I think you will find that as a species we are far less prone to folly than we once were."

Davout looked at his sib grimly. "You are suggesting that I undergo this technique?"

"It is called Lethe."

"That I undergo Lethe? Forget Katrin? Or forget what I feel for her?"

Silent Davout slowly shook his grave head. "I make no such suggestion."

"Good."

The youngest Davout gazed steadily into the eyes of his older twin. "Only you know what you can bear. I merely point out that this remedy exists, should you find your anguish beyond what you can endure."

"Katrin deserves mourning," Davout said.

Another grave nod. "Yes."

"She deserves to be remembered. Who will remember her if I do not?"

"I understand," said Silent Davout. "I understand your desire to feel, and the necessity. I only mention Lethe because I comprehend all too well what you endure now. Because"-he licked his lips-"I, too, have lost Katrin."

Davout gaped at him. "You-" he stammered. "She is-she was killed?"

No. His sib’s face retained its remarkable placidity. "She left me, sixteen years ago."

Davout could only stare. The fact, stated so plainly, was incomprehensible.

"I-" he began, and then his fingers found another thought. What happened?

"We were together for a century and a half. We grew apart. It happens."

Not to us it doesn’t! Davout’s mind protested. Not to Davout and Katrin!

Not to the two people who make up a whole greater than its parts. Not to us. Not ever.

But looking into his sib’s accepting, melancholy face, Davout knew that it had to be true.

And then, in a way he knew to be utterly disloyal, he began to hope.

"Shocking?" said Old Davout. "Not to us, I suppose."

"It was their downloads," said Red Katrin. "Fair Katrin in particular was careful to edit out some of her feelings and judgments before she let me upload them, but still I could see her attitudes changing. And knowing her, I could make guesses by what she left out… I remember telling Davout three years before the split that the relationship was in jeopardy."

"The Silent One was still surprised, though, when it happened," Old Davout said. "Sophisticated though he may be about human nature, he had a blind spot where Katrin was concerned." He put an arm around Red Katrin and kissed her cheek. "As I suppose we all do," he added.

Katrin accepted the kiss with a gracious inclination of her head, then asked Davout, "Would you like the blue room here, or the green room upstairs? The green room has a window seat and a fine view of the bay, but it’s small."

"I’ll take the green room," Davout said. I do not need so much room, he thought, now that I am alone.

Katrin took him up the creaking wooden stair and showed him the room, the narrow bed of the old house. Through the window, he could look south to a storm on Chesapeake Bay, bluegray cloud, bright eruptions of lightning, slanting beams of sunlight that dropped through rents in the storm to tease bright winking light from the foam. He watched it for a long moment, then was startled out of reverie by Katrin’s hand on his shoulder, and a soft voice in his ear.

"Are there sights like this on other worlds?"

"The storms on Rhea were vast," Davout said, "like nothing on this world. The ocean area is greater than that on Earth, and lies mostly in the tropics-the planet was almost called Oceanus on that account. The hurricanes built up around the equatorial belts with nothing to stop them, sometimes more than a thousand kilometers across, and they came roaring into the temperate zones like multi-armed demons, sometimes one after another for months. They spawned waterspots and cyclones in their vanguard, inundated whole areas with a storm surge the size of a small ocean, dumped enough rain to flood an entire province away… We thought seriously that the storms might make life on land untenable."

He went on to explain the solution he and Katrin had devised for the enormous problem: huge strings of tall, rocky barrier islands built at a furious rate by nanomachines, a wall for wind and storm surge to break against; a species of silvery, tropical floating weed, a flowery girdle about Rhea’s thick waist, that radically increased surface albedo, reflecting more heat back into space. Many species of deep-rooted, vinelike plants to anchor slopes and prevent erosion, other species of thirsty trees, adaptations of cottonwoods and willows, to line streambeds and break the power of flash floods.

Planetary engineering on such an enormous scale, in such a short time, had never been attempted, not even on Mars, and it had been difficult for Katrin and Davout to sell the project to the project managers on the Cheng Ho. Their superiors had initially preferred a different approach, huge equatorial solar curtains deployed in orbit to reflect heat, squadrons of orbital beam weapons to blast and disperse storms as they formed, secure underground dwellings for the inhabitants, complex lock and canal systems to control flooding… Katrin and Davout had argued for a more elegant approach to Rhea’s problems, a reliance on organic systems to modify the planet’s extreme weather instead of assaulting Rhea with macro-tech and engineering. Theirs was the approach that finally won the support of the majority of the terraforming team, and resulted in their subsequent appointment as heads of Beagle’s terraforming team.

"Dark Katrin’s memories were very exciting to upload during that time," said Katrin the Red. "That delirious explosion of creativity! Watching a whole globe take shape beneath her feet!" Her green eyes look up into Davout’s. "We were jealous of you then. All that abundance being created, all that talent going to shaping an entire world. And we were confined to scholarship, which seemed so lifeless by comparison."

He looked at her. Query "Are you sorry for the choice you made? You two were senior: you could have chosen our path if you’d wished. You still could, come to that."

A smile drifts across her face. "You tempt me, truly. But Old Davout and I are happy in our work-and besides, you and Katrin needed someone to provide a proper record of your adventures." She tilted her head, and mischief glittered in her eyes. "Perhaps you should ask Blonde Katrin. Maybe she could use a change."