In the dense fog of London, Kitty Killigrew hears a clandestine conversation before her sapphire necklace is stolen by a wily young man. It is up to Detective Haggerty to find the culprit. But as he gets closer and closer to the thief, things become more complicated than he expected. Kitty Killigrew's new romantic interest may be involved; her sapphires may have been lost forever. And it all comes back to those voices in the fog.Fog.A London fog, solid, substantial, yellow as an old dog's tooth or a jaundiced eye. You could not look through it, nor yet gaze up and down it, nor over it; and you only thought you saw it. The eye became impotent, untrustworthy; all senses lay fallow except that of touch; the skin alone conveyed to you with promptness and no incertitude that this thing had substance. You could feel it; you could open and shut your hands and sense it on your palms, and it penetrated your clothes and beaded your spectacles and rings and bracelets and shoe-buckles. It was nightmare, bereft of its pillows, grown somnambulistic; and London became the antechamber to Hades, lackeyed by idle dreams and peopled by mistakes.There is something about this species of fog unlike any other in the world. It sticks. You will find certain English cousins of yours, as far away from London as Hong-Kong, who are still wrapt up snugly in it. Happy he afflicted with strabismus, for only he can see his nose before his face. In the daytime you become a fish, to wriggle over the ocean's floor amid strange flora and fauna, such as ash-cans and lamp-posts and venders' carts and cab-horses and sandwich-men. But at night you are neither fish, bird nor beast.The night was May thirteenth; never mind the year; the date should suffice: and a Walpurgis night, if you please, without any Mendelssohn to interpret it.That happy line of Milton's-"Pandemonium, the high capital of Satan and his peers"-fell upon London like Elijah's mantle. Confusion and his cohort of synonyms (why not?) raged up and down thoroughfare and side-street and alley, east and west, danced before palace and tenement alike: all to the vast amusement of the gods, to the mild annoyance of the half-gods (in Mayfair), and to the complete rout of all mortals a-foot or a-cab. Imagine: militant suffragettes trying to set fire to the prime minister's mansion, Siegfriedbeing sung at the opera, and a yellow London fog!The press about Covent Garden was a mathematical problem over which Euclid would have shed bitter tears and hastily retired to his arbors and citron tables. Thirty years previous (to the thirteenth of May, not Euclid) some benighted beggar invented the Chinese puzzle; and tonight, many a frantic policeman would have preferred it, sitting with the scullery maid and the pantry near by. Simple matter to shift about little blocks of wood with the tip of one's finger; but cabs and carriages and automobiles, each driver anxious to get out ahead of his neighbor!-not to mention the shouting and the din and discord of horns and whistles and sirens and rumbling engines!"It's hard luck," said Crawford, sympathetically. "It will be half an hour before they get this tangle straightened out.""I shouldn't mind, Jim, if it weren't for Kitty," replied his wife. "I am worried about her.""Well, I simply could not drag her into this coupé and get into hers myself. She's a heady little lady, if you want to know. As it is, she'll get back to the hotel quicker than we shall. Her cab is five up. If you wish, I'll take a look in and see if she's all right."