Alive and well despite the widely published accounts of her death, diva Irene Adler and her dashing husband Godfrey Norton are taking coffee with their friend Nell Huxleigh in a Parisian sidewalk café when a stranger dressed in Oriental garb falls at their feet. It is not Irene’s beauty that has felled him, but a dose of poison— and even more surprisingly, the friends learn as he recovers that he is an Englishman! The mysterious young man informs them that he is seeking a Dr. Watson who tended his wounds at the disastrous battle of Maiwand, a man whose life he says is now in mortal danger.

The hunt is on and their search will lead them to a command performance for the Empress of all the Russias and to Sarah Bernhardt, into a channel steamer and at last to the doorstep of 221 Baker Street, where they will discover deadly secrets both past and present.