Shadow of the Yangtze (Ghosts of Shanghai, Bk. 2)

Ruby - a Western girl who feels more Chinese than English - and her friend Charlie must follow the Yangtze hundreds of miles upriver, travelling by Chinese junk and rogue steamer, through bandit and ghost haunted countryside - doggedly tracking Moonface as he spirits Charlie's sister Fei off to his home village. Everything is in flux around them: civil war pulsing, with Nationalists, Communists and warlord bandits struggling for control. The river rises and falls, villages spring up and are gone again.

Ruby and Charlie brave a shipwreck and a gunbattle and then take a perilous cliff path to Moonface's lair.