In a place like the Rennoc, run as an apartment hotel, the guests change quite frequently, and it was some task to keep track of all of them, particularly when there were three girls working in the daytime, though only one was on at night. They took it by turns--each one working one week in four at night and the other three holding down the job from eight to six. So, as it happened, Virginia did not see Dave Carroll until he had been there nearly a month. He blew in from Washington early one evening and straightway absented himself from the hotel until sometime around seven the following morning, following the schedule right through, every night. Did you ever know Carroll? He and I worked together on the Farron case out in St. Louis, the one where a bookmaker at the races tipped us off to the biggest counterfeiting scheme ever attempted in this country, and after that he took part in a number of other affairs, including the one which prevented the Haitian revolution in nineteen thirteen. Dave wasn't what you would call good-looking, though he did have a way with women. The first night that he came downstairs--after a good day's sleep--and spotted Virginia Lang on the switchboard, he could have been pardoned for wandering over and trying to engage her in a conversation. But the only rise he got was from her eyebrows. They went up in that "I-am-sure-I-have-never-met-you" manner which is guaranteed to be cold water to the most ardent male, and the only reply she vouchsafed was "What number did you wish?" "You appear to have mine," Dave laughed, and then asked for Rector 2800, the private branch which connected with the Service headquarters. When he came out of the booth he was careful to confine himself to "Thank you" and the payment of his toll. But there was something about him that made Virginia Lang feel he was "different"--a word which, with women, may mean anything--or nothing. Then she returned to the reading of her detective story, a type of literature to which she was much addicted. Carroll, as you have probably surmised, was one of the more than twoscore Government operatives sent to New York to work on the von Ewald case. His was a night shift, with roving orders to wander round the section in the neighborhood of Columbus Circle and stand ready to get anywhere in the upper section of the city in a hurry in case anything broke. But, beyond reporting to headquarters regularly every hour, the assignment was not exactly eventful. The only thing that was known about von Ewald at that time was that a person using such a name--or alias--was in charge of the German intrigues against American neutrality. Already nearly a score of bomb outrages, attempts to destroy shipping, plots against munition plants, and the like had been laid at his door, but the elusive Hun had yet to be spotted. Indeed, there were many men in the Service who doubted the existence of such a person, and of these Carroll was one.