1899 Paris is roiling over the infamous "Dreyfus Affaire". From the Chamber of Deputies to the popular press to café society, the rumor is that Captain Dreyfus, convicted of treason in 1894 and sentenced to banishment from France for life, is to be given a new trial. However, amidst the growing clamor on both sides, there are those who will stick at nothing to prevent the truth from coming out. Meanwhile, following the Milverton case ("The worst man in London"), Holmes and Watson are keeping a low profile. Upon returning from a rare evening out they are accosted by a young army officer bringing them a letter imploring them to come to the aid of Captain Dreyfus. Glad to be away from London, but at the same time dreading becoming embroiled in the Dreyfus Affaire, they book into the new Ritz Hotel where they are reunited with old friends Cesár Ritz and Auguste Escoffier. But Holmes and Watson face two challenges. First, their mission must remain secret; if discovered, the British Government will disavow any knowledge of their purpose. And, they soon learn that the Dreyfus case has roots in the Franco-Prussian war of 1870 and now threatens to bring down the French Government and perhaps bring on a pan-European war that must inevitably involve Britain as well.