Beijing detective Li Yan, now based at the Chinese embassy in Washington, is dispatched to find out how his fellow countrymen died in a sealed refrigeration unit in southern Texas. Then he finds himself face-to-face with American pathologist Margaret Campbell, the woman who walked out of China, and his life, to return to the U.S.

Tasked to work together again to investigate the $100 million trade in illegal Chinese immigrants that led to the tragedy in Texas, they discover that the immigrants were unwitting carriers of a deadly cargo. And still wrestling with the demons of their pasts, Li and Margaret find themselves racing against time to defuse a biological time-bomb that threatens to wipe out not only their future, but that of humankind.