“Billy is a dear boy,” she said, “and his friend seems a thoroughly nice fellow, but I couldn’t think of letting you go to a dance with them out in some suburb of Paris, unless I knew you were in charge of a sensible, careful chaperon. Mr. Trevelyan’s sister may or may not answer the description. We have no idea how old she is, or what sort of person she is, or whether she even understands from her brother that you would be in her charge. Evidently you wouldn’t be while you were going and coming. Oh, it’s quite impossible.”