"The success of any ramble, picnic, excursion, or small party," he added pensively, "depends entirely on arithmetic. No matter of what elements the party be composed, the addition or subtraction of one may spoil all," a pronouncement heartily endorsed by Ermengarde, as expressing her own feelings on the subject, though she had not guessed at what person's subtraction he was obscurely hinting as ruinous to his enjoyment. Nor did she for a moment suspect that, in arranging the Monte Carlo afternoon for two performers only, she had sadly diminished poor Mr. Welbourne's pleasure. Since the Carnival, the woman of mystery had not been asked to accompany Mrs. Allonby anywhere, nor had the two ladies once helped each other to dress or exchanged small talk from their adjoining rooms, which communicated by a door. A woman who received jewellery from one mask and letters from another, and held conversations and clandestine meetings with at least two suspicious male characters, was not a desirable acquaintance for a grass widow and a mother of unimpeachable respectability. Yet Ermengarde's heart misgave her when she met the silent question of Agatha's melancholy eyes at any approach to companionship on her part meeting with repulse. She hated herself especially the morning after the Cap Martin excursion when, with the full intention of spending the afternoon at Monte Carlo, she declined a mountain walk with Agatha on the ground that it was less tiring to bask in the sunny garden at home. "Then I think I will run down to Mentone," Agatha said, in a confidence untouched by suspicion. "I have an invalid friend in the place who likes me to come in to luncheon sometimes." After all, could there be anything more restful than these quiet lounges by train from spacious halls of leisure, called Gares in that country? the thin man and Ermengarde wondered, as they sauntered about the clean and airy emptiness of Mentone Station, and chanced to take seats in a train that happened to be strolling in the direction of France, and was entirely composed of first-class carriages, well-cushioned, and provided with antimacassars of spotless crochet-work. Other people as casually strolled over and rested, as if by happy chance, in the clean and comfortable carriages, and after some time, enjoyably spent with a prospect of sea and mountain and near view of palm and garden and sunny street, it seemed to occur to the person lounging upon the engine to propel the string of carriages gently in the direction of France, and they glided through the now familiar but never-lessening enchantment of rich scenery between mountain and sea, always plunging into the tunnelled darkness whenever a fairy headland ran out into blue and foam-fringed bays. But what talk they heard on this fairy progress! The tongues were many, but the subject one alone. For example-- "You'll hardly be at the tables to-night, Ethel?"