The Chinese label

When the United States Treasury learns from secret sources that two famous diamonds, stolen from the Sultan’s sash, will probably be smuggled into this country, it sets its machinery quickly to work.

Napier, of the Secret Service, is the agent chosen, and San Antonio is selected as the likeliest place in which to unearth the plot. Napier’s task is a hard one, but with skill he picks up clue after clue from insignificant happenings, implicating Chinese and Mexicans, and American arms officer, and an international spy.

All are linked with the two diamonds, which are supposed to be concealed in a can of opium bearing a Chinese label.