Rising in the Mongolian mountains and flowing through Siberia to the Pacific, the Amur river forms the tense border between Russia and China. This is the most densely fortified frontier on Earth.

In his eigthieth year, Colin Thubron takes a dramatic and often treacherous journey from the Amur's secret source to its giant mouth, covering almost 3,000 miles. Harassed by injury and by arrest from the local police, he makes his way along both the Russian and Chinese shores. By the time he reaches the river's desolate end, a whole, pivotal world has come alive.