A professional case of great gravity was engaging my own attention at the time, and the whole of next day I was busy at the bedside of the sufferer. It was not until close upon six o’clock that I found myself free and was able to spring into a hansom and drive to Baker Street, half afraid that I might be too late to assist at the dénouement of the little mystery. I found Sherlock Holmes alone, however, half asleep, with his long, thin form curled up in the recesses of his armchair. A formidable array of bottles and test-tubes, with the pungent cleanly smell of hydrochloric acid, told me that he had spent his day in the chemical work which was so dear to him.