had done before, and simply continue to move backward, to Acho's emergence from Diko's womb, back to Diko's childhood home and her own birth. Acho's disappearance had had too many reverberations, not just in his mother's life but, through her, in the lives of the whole village, for Tagiri to leave the mystery of his disappearance unsolved. Diko never knew what happened to her boy, but Tagiri had the means to find out. And besides, even though it meant changing direction and searching forward in time for a while, tracking, not a woman, but a boy, it was still a part of her backward search. She would find what it was that took Acho and caused Diko's endless grief.
There were hippos in the waters of the Koss in those days, though rarely this far upriver, and Tagiri dreaded seeing what the villagers assumed -- poor Acho broken and drowned in the jaws of a surly hippopotamus.
But it was not a hippo. It was a man.
A strange man, who spoke a language unlike any that Acho had heard -- though Tagiri recognized it at once as Arabic. The man's light skin and beard, his robe and turban, all were intriguing to the nearly naked Acho, who had seen only people with dark brown skin, except when a group of blue-black Dinkas came hunting up the river. How was such a creature as this possible? Unlike other children, Acho was not one to turn and flee, and so when the man smiled and talked his incomprehensible babble (Tagiri knew he was saying, "Come here, little boy, I won't hurt you") Acho stood his ground, and even smiled.
Then the man lashed out with his stick and knocked Acho senseless to the ground. For a moment the man seemed concerned that he might have killed the boy, and he was satisfied to find Acho was still breathing. Then the Arab folded the unconscious child into fetal position and jammed his small body into a bag, which he hoisted over his shoulder and carried back down the riverbank, where he joined two other companions, who also had full bags.
A slaver, Tagiri realized at once. She had thought they did not come this far. Usually they bought their slaves from Dinkas down at the White Nile, and the Dinka slavers knew better than to come into the mountains in groups so small. Their method was to raid a village, kill all the men, and take the small children and the pretty women off for sale, leaving only the old women behind to keen for them. Most of the Muslim slavers preferred to trade for slaves rather than to do their own kidnapping. These men had broken with the pattern. In the old marketeering societies that nearly ruined the world, thought Tagiri, these men would have been viewed as vigorous, innovative entrepreneurs, trying to make a bit more profit by cutting out the Dinka middlemen.
She meant to resume her backward watching then, returning to the life of Acho's mother, but Tagiri found that she could not do it. The computer was set to find new vantage points tracking Acho's movements, and Tagiri did not reach out and give the command that would have returned to the earlier program. Instead she watched and watched, moving forward through time to see, not what caused all this, but where it led. What would happen to this bright and wonderful boy that Diko loved.
What happened at first was that he was almost liberated -- or killed. The slavers were stupid enough to have captured slaves on their way up the river, even though there was no way to return except by passing near the very villages where they had already kidnapped children. At a village farther downstream, some Lotuko men in full warrior dress ambushed them. The other two Arabs were killed, and since their sacks contained the only children the Lotuko villagers cared about -- their own -- they allowed the slaver who carried Acho on his back to escape.
The slaver eventually found his way to the village where two black slaves of his were keeping the camels. Strapping the bag containing Acho onto the camel, the surviving members of the slaving party got under way at once. To Tagiri's disgust, the man didn't so much as open the bag to see if the boy was still alive.
And so the journey down the Nile continued, all the way to the slave market of Khartoum. The slaver would open the bag