He had heard, and dimly believed, that it was morally wrong, and, still worse, quite bad form, to take notice of anonymous letters. But this one must be different, it seemed to him, from any other which anybody had ever received. Duty to his employers and duty to the one thing he really loved was above any other duty; and for fear of losing forever an immense, an unhoped-for advantage, which might possibly be gained, he dared not ignore the letter. At all events, he had told himself, no matter what he might decide later, it was just as well that he had accepted the invitation to Valley House. Perhaps someone--he could not think who--was playing a stupid practical joke, with the object of getting him there. But he would risk that and go, and let his conduct shape itself according to developments. For instance, if his eyes were able to detect the small detail mysteriously mentioned in the letter, he would feel bound to act as it suggested; yes, bound to act--but how unpleasant it would be! And the worst of the whole unpalatable affair was that if he _did_ act in that suggested way, and if he accomplished what he might, with dreadful deftness, be supposed to accomplish, it would be the moment when perhaps he might be fooled. _If_ the letter were written by a practical joker, he would be made to look ridiculous in the eyes of all who were in the secret. And that thought brought him back to the question which over and over he asked in his mind. Who could have written the anonymous letter? It must be someone acquainted with him, or with his profession; someone who knew the Nelson Smiths and the Annesley-Setons well enough to be aware that there was to be an Easter party at Valley House. The writer hinted in vague terms that he was a private detective aware of certain things, yet so placed that he could have no handling of the affair, except from a distance, and through another person. He pretended a disinterested desire to serve Ruthven Smith, and signed himself, "A Well Wisher"; but the nervous recipient of the advice felt that his correspondent was quite likely to be of the class opposed to detectives. What if there were some scheme for a robbery on a vast scale at Valley House, and this letter were part of the scheme? What if the band of thieves supposed to be "working" lately in London should try to make him a cat's paw in bringing off their big haul? This was a terrifying idea, and more feasible than the one suggested by the anonymous writer, that Mrs. Nelson Smith should--oh, certainly it seemed the wildest nonsense! Still, there was his duty to the Van Vrecks. They must be considered ahead of everything! So Ruthven Smith, nervous as a rabbit who has lost its warren, travelled down to Devonshire on Saturday afternoon, invited to stay at Valley House till Tuesday.