Engineer He Min transmigrates to the final years of the Qin dynasty. The great Qin war machine is nearing the end of its campaigns on all fronts, and society has begun to grind to a halt. The First Emperor has died, while Li Si, the Legalist who holds the reins of power, is consumed by the struggle for the throne at court and turns a blind eye to the resistance crushed beneath the people's feet. He Min's arrival brings modern diseases, two thousand years ahead of their time, into ancient society, triggering the infamous great plague at the end of Qin. Using his modern medical knowledge, He Min risks his life to save people across the land. His skill earns the admiration of the Mohists, whom the Qin dynasty has thoroughly suppressed, and they invite him to treat their current Grand Master for the plague. But there is no turning back the tide. As the Grand Master lies dying, he hears He Min tell of how modern technology benefits humanity, and passes away with a smile. He appoints He Min as his successor. Taking up the charge, He Min leads the surviving Mohists and plans to rebuild their home.
In the struggle for the throne, all of the First Emperor's more than ten children are killed, and his eldest son Fusu is ordered to commit suicide. Chu's plan to reform Qin collapses, while the Xiang uncles and nephews bide their time and build up their strength for an uprising.
The garrison troops rebel, Hangu Pass falls, and the realm descends into chaos. As the former states rise in the war to restore their kingdoms, He Min and the Mohists, hidden away in the mountains, are swept by the times into a world at war. Adrift in a turbulent age, they carry both the Mohists' deadliest blade and the most potent remedy for governing the world. Their ideals of universal love, opposition to aggression, and equality for all have never been buried.
