In this alternate history novel, the Black Death kills virtually all of Europe's population in the 14th century, erasing Christian civilization from the world stage. The seven centuries that follow unfold under the dominance of Islam, China, India, and the Indigenous nations of the Americas. Connecting these disparate eras is a small group of souls, a jati, a karmic family in Buddhist cosmology who reincarnate together life after life, struggling toward justice and meeting between deaths in the bardo, the Tibetan Buddhist realm of transition between lives.
The story begins when Bold Bardash, a half-Tibetan, half-Mongol horseman in Temur the Lame's army, scouts westward and discovers that the Magyar people appear to have died of plague, though his party cannot be certain. When Bold reports this, Temur orders him killed for bringing a curse, but a lightning bolt kills Temur instead, and Bold flees west through the depopulated continent. Muslim sailors capture him on the coast and sell him into slavery. In East Africa, Bold and a young African boy named Kyu are purchased by officers of the Chinese treasure fleet. Aboard ship, officers forcibly castrate Kyu, and Bold nurses him through a dangerous fever. In China, Kyu murders their enslaver, sets fire to the neighborhood, and forces Bold north to Beijing. Consumed by hatred for the empire that mutilated him, Kyu enters the imperial eunuch service and schemes to destabilize the court. When the Yongle Emperor dies and his successor turns against the eunuchs, Kyu is stabbed to death, and Bold is killed shortly after. In the bardo, Bold explains that they belong to a jati, a cluster of souls bound together through successive incarnations, and both are reborn.
The jati's next lives unfold in India, where a village girl named Kokila poisons the corrupt headman and his son after they cause her friend Bihari's death. Kokila's soul returns as Kya, a tigress who rescues a young traveler from an ambush. The traveler reincarnates as Bistami, a Sufi scholar who becomes an advisor to the Mughal Emperor Akbar. After palace intrigues, Akbar exiles Bistami to Mecca, where he joins a caravan led by Sultan Mawji Darya and his wife, Sultana Katima. They cross the Pyrenees into the empty lands of former Europe and found the city of Baraka on the Atlantic coast, where Katima advocates for women's equality based on Quranic principles. When Mawji dies and invaders threaten, Bistami convinces Katima to flee north, where they establish the city of Nsara.
A Chinese invasion fleet bound for Japan is swept east across the Pacific by a prolonged calm. Admiral Kheim and his crew discover a great bay on an unknown continent and befriend the Miwok people, peaceful hunter-gatherers. A young Miwok girl they name Butterfly becomes their translator. When smallpox from the Chinese sailors begins killing the Miwok, Kheim takes Butterfly aboard to protect her and sails south to a gold-roofed mountain empire. Priests attempt to sacrifice Butterfly atop a volcano, but Kheim shoots the executioner with a flintlock pistol and rescues her. During the return voyage, Butterfly dies from injuries sustained in a typhoon. Back in China, Kheim tells the emperor that the greatest treasure of the new continent "is already lost," framing the entire voyage as moral tragedy.
In the khanate of Bokhara, the alchemist Khalid Ali Abu al-Samarqandi attempts to fake the transmutation of lead into gold before the local khan. The fraud is exposed and Khalid's right hand is chopped off. His son-in-law Bahram and the Tibetan glassblower Iwang pull Khalid out of despair by reigniting his scientific curiosity. Together they drop weights to disprove Aristotle, build vacuum pumps, study optics with prisms, and formulate a mathematical law of universal gravitation. The khan's secretary Nadir Divanbegi takes Bahram's wife Esmerine and their children hostage to compel weapons research. Khalid develops poison gas shells and rifled cannons. The Qing dynasty's Manchu expansion threatens from the east, and plague arrives in the region. The hostages are returned already infected, and Esmerine, the children, Khalid, and Iwang all die. In the bardo, the jati argues bitterly: Khalid demands justice, Bahram insists on love, and Iwang proposes they must build their own world without relying on the gods.
A Japanese ronin, or masterless warrior, named Fromwest arrives among the Hodenosaunee, the confederacy of nations in eastern North America. Raised to chief, he warns the council that Chinese and Muslim empires are approaching their shores and urges them to learn metalworking and gunmaking.
In Qing-dynasty China, the scholarly Widow Kang Tongbi takes in a wandering Buddhist monk named Bao Ssu and feels an inexplicable recognition. After Bao is arrested during a soul-stealing panic, subjected to torture, and dies in prison of a fever, a Muslim doctor from Iran named Ibrahim ibn Hasam helps Kang access memories of past lives through hypnotic meditation. They recognize each other from previous incarnations and marry, traveling to the frontier city of Lanzhou to reconcile Islam and Confucianism. Kang writes about the Four Great Inequalities: the subjugation of farmers by warriors, women by men, children by parents, and enslaved peoples by dominant groups. In old age, Ibrahim writes that humanity remains in prehistory until justice prevails. Kang responds with a poem affirming that what she liked most was "the rice and the salt" of daily life.
The narrative accelerates through an era of great progress. The Ottoman Empire falls to steam-powered warships from Travancore, a modernizing Indian state. On the west coast of Yingzhou (the Americas), Japanese and Chinese settlers compete for territory. Tensions among China, Islam, and the Indian League, a major political and military alliance, escalate into a catastrophic global conflict called the Long War, lasting decades. Three Chinese soldiers embody the jati in the trenches of the Gansu Corridor, where the front has barely moved in 60 years: the sardonic Kuo, the scholarly Iwa, and the steadfast Bai. After Kuo is killed by a shell, his ghost appears to Bai and declares they are all already dead. The armies eventually cross the Himalayas and link with Indian forces, but at Bodh-Gaya, where the Buddha received enlightenment, the soldiers find the sacred Bodhi Tree destroyed by artillery. Iwa suggests there may be no afterlife at all, that this one life is everything.
In postwar Nsara, a young woman named Budur escapes her father's harem in the Alpine city of Turi and follows her aunt Idelba, a physicist, to the Atlantic coast. Budur studies with the historian Kirana Fawwaz, who argues that Islam's patriarchal distortions of the Quran cost Muslims the war by keeping half the population subjugated. Idelba reveals that her atomic research on the heavy element alactin, analogous to uranium, could theoretically produce an enormously powerful bomb, and insists all the world's scientists must know simultaneously so no single nation gains advantage. After Idelba's death, Budur carries this mission to an international conference in Isfahan. A military coup in Nsara is defeated when Budur leads war veterans blinded in the conflict into the palace square, and a Hodenosaunee fleet blockades the harbor until the generals stand down.
In the final book, the young Bao Xinhua follows the charismatic revolutionary Kung Jianguo through China's civil war against its military government. They organize farmers using the communal theories of the philosopher Zhu Isao and prevail, but Kung is assassinated on the day of triumph, dying in Bao's arms with the words "Go on." Decades later, Bao retires to a small California valley town to teach history under oak trees and tend a garden. He reflects that reincarnation persists in children, in cultural memory, and in the way future generations model their lives on those who came before. A new student named Kali joins his class, skeptical and sharp-eyed, and Bao recognizes he will learn from her, signaling the jati's cycle continuing into yet another life.