This is a sci fi story about changing the future by changing an event in the past.
The story is therefore told in two different time periods: in a future, many centuries from our own time; and in the 15th century, the time of Christopher Columbus.
For me, the most interesting part of the story was how the two time periods become tightly connected through the Pastwatch Project: scientists, scholars and historians working together, using increasingly advanced time machines to visualize Earth’s past in great detail. Eventually they build time travel machines: to travel back to a given time in the past, to change an event, and to thereby change the future.
The story begins centuries in the future: Earth has been devastated by war and natural disasters. It has become vital for people to share resources, to rebuild for a better future by learning from the past.
As I read the story, two major characters emerged: Tagiri and her daughter Diko. Both are historians, in Juba, North Africa. Tagiri’s Pastwatch research leads her into the history of slavery in Africa, in the Americas and the slave trade across the Atlantic. The turning point for her comes when she views the discovery voyage of Christopher Columbus, and the Spanish attack on Hispaniola. Tagiri realizes that a woman from that past is able to see her, and is seeking her help. How can the past be changed to stop the Spanish conquests and slavery in Central America?
Diko becomes actively involved in the research group. There are intensive discussions on whether it would be right or wrong to prevent or change Columbus’ voyage to the Caribbean. Ultimately, the researchers decide to put into action a plan to let Columbus sail to the Caribbean, but stop his return to Spain for several years.
Diko and two other Pastwatch researchers, Hunahpu and Kemal, travel separately to the past, at different times. Each is aware that their actions will change their own future, and of others in the future. They put their plan into action: Columbus loses all his ships in the Caribbean. He is stranded. Diko and her team thus prevent him from returning to Spain for several years. And in that time, the Central America kingdoms continue to develop their civilizations, and not be devastated by European conquest and slavery.
With Diko’s help, Columbus eventually learns to live among the peoples of Central America. He eventually returns to Spain, in ships built and commanded by the people of Central America. The Europeans and Central Americans meet, on equal terms, in a peaceful way.
The novel ends with a postscript: In the changed future, Earth is utopian.