Agatha Christie 
The Lost Mine [EPUB ebook] 

In Agatha Christie’s short story, 'The Lost Mine, ’ Poirot investigates the suspicious disappearance of a Chinese businessman in London. Suspicion is focused on two Englishman, one of whom has an alibi and another who was in an opium den the night of the disappearance. A clear-cut case for Poirot soon becomes murky however. This short story originally appeared in the November 21, 1923 issue of The Sketch magazine.