The Adventure of the Amateur Commission Agent

When my inner self goes wrong, my bangle turns dusky.' She held up her right hand with an Indian silver bangle on it; and sure enough, it was tarnished with a very thin black deposit. 'My soul is ailing now, ' she said in a comically serious voice. 'But it is seldom so in Switzerland. The moment I land in England the bangle turns black and remains black till I get back to Lucerne again.'