CHAPTER X DOROTHY'S PROMISEBUT though the men from Philadelphia could not reach White Birches until seven o'clock, the doctor and the electrical engineer arrived during the afternoon hours.
Their information proved of no help in solving the mystery, but rather deepened it.
After a thorough and careful examination of the burglar alarm and all its attachments, annunciators and indicators, the electrical expert pronounced it the most marvelous affair of its kind he had ever seen. He said that it was in perfect order, and that, owing to its wonderful and ingenious mechanism, it was positively impossible that anyone should have gone out of the house between 12.30 a.m., when it was turned on, and 7.30 a.m., when Driggs had turned it off. The man staked his entire reputation as an electrical ex
