The musical programme was interesting and varied, but during the second half of the concert the cheerfulness of the scene was sadly marred by the ever-increasing fog which crept in from without, filling the vast interior with a gloom against which the many lights seemed powerless to contend. Dr Trevor began to feel a little nervous about the safety of his party, and suggested making a move before the end of the concert, but Miss Beveridge insisted that she and her friend needed no escort home. "It would have to be a very bad fog to frighten us. We are accustomed to going about town in all weathers," she declared, and this was so obviously the case that it seemed affectation to protest. The doctor therefore explained that as he was in charge of Cynthia he wished to allay her mother's natural anxiety as soon as possible, and the young people bade farewell to their guests of the afternoon and hurried downstairs. Early though it was, hundreds of people seemed to have been inspired by the same fears, for the stairway was thronged and the passages downstairs were becoming momentarily blocked. Dr Trevor tucked Cynthia's hand through his arm. "Look after your sister, Miles," he cried, turning a quick glance over his shoulder. "I'm afraid it's very thick. Keep close behind me if you can. In any case make the best of your way home." A moment later they passed through the doorway into a world of black gloom, in which phantom shapes at one moment pressed against one, and at the next vanished utterly from sight. Betty gave a little cry of dismay, for, London-bred as she was, never before had she been out of doors in such an impenetrable fog. She put out her hand towards the spot where Miles had stood a moment before, but her fingers gripped nothing more substantial than air. She gave a quick leap forward, and clutching at a shadowy coat-sleeve shook it violently, calling out in accents half-frightened, half-angry-- "Miles, how horrid of you! You must not stalk on ahead like that! I shall be lost, and then what will become of me? For pity's sake keep hold of my arm!" She had walked a few paces forward as she spoke, but now she stopped short, in response to a determined movement of the arm to which she clung. Betty glanced upwards in surprise; she could not see the face so near to her arm, but the blood chilled in her veins as a strange voice answered slowly-- "But--I'm sorry, but I do not happen to be Miles!" CHAPTER SIXTEEN. LOST IN THE FOG.