The tale opens in the South Seas, near an island cloaked in mystery. There, Gregory Sallust enters the service of the lovely lady A-lu-te. Together with the jovial Kâo Hsuan and the earnest Mandarin Tsai-Ping, they set off to find the lost heir to the Imperial Throne of China. Their search takes them to San Francisco's Chinatown, then back across the Pacific and through the heart of China up to the borders of Mongolia. After they have travelled 10,000 miles we read: 'At last they had reached their journey's end. Since they had set out three people had died unexpectedly and horribly; and Gregory had had five narrow escapes from death.'

Yet that is only halfway through the story. They have still to beard the man who is said to have carried off the lost Princess, and who lives like a feudal Baron in the great House of Lin.