The Vanished Messenger by E. Phillips Oppenheim

Hamel sat alone upon the terrace, his afternoon coffee on a small table in front of him. His eyes were fixed upon a black speck at the end of the level roadway which led to the Tower. Only a few minutes before, Mr. Fentolin, in his little carriage, had shot out from the passage beneath the terrace, on his way to the Tower. Behind him came Meekins, bending over his bicycle. Hamel watched them both with thoughtful eyes. There were several little incidents in connection with their expedition which he scarcely understood.

Then there came at last the sound for which he had been listening, the rustle of a skirt along the terraced way. Hamel turned quickly around, half rising to his feet, and concealing his disappointment with difficulty. It was Mrs. Seymour Fentolin who stood there, a little dog under each arm; a large hat, gay with flowers, upon her head. She wore patent shoes with high heels, and white silk stockings. She had, indeed, the air of being dressed for luncheon at a fashionable restaurant. As she stooped to set the dogs down, a strong waft of perfume was shaken from her clothes.