Does your husband know the details of that trip to Fond du Lac? He might be interested in what Hastings has to tell him. The second, which arrived some ten days later, announced: The photograph of the register of a certain hotel in Fond du Lac for June 8 might be of interest to your husband--who can tell? That was all there was to them, but it doesn't take an expert in plot building to think of a dozen stories that could lie back of that supposedly clandestine trip on the eighth of June. Tyson didn't go into particulars at the time. He contented himself with turning the letters over to the department, with the request that the matter be looked into at once. Said that his wife had handed them to him and that he knew nothing more about the matter. All that the postal authorities could do at the time was to instruct him to bring in any subsequent communications. But, as the letters stopped suddenly and Tyson absolutely refused to state whether he knew of anyone who might be interested in causing trouble between his wife and himself, there was nothing further to be done. Tracing a single letter, or even two of them, is like looking for a certain star on a clear night--you've got to know where to look before you have a chance of finding it--and the postmark on the letters wasn't of the least assistance. Some three or four weeks later a similar case cropped up. This time it was a woman who brought in the letters--a woman who was red-eyed from lack of sleep and worry. Again the communications referred to a definite escapade, but still they made no open demand for money. By the time the third case cropped up the postal authorities in Madison were appealing to Washington for assistance. Before Bolton and Clarke, the two inspectors originally assigned to the case, could reach the Wisconsin capital another set of the mysterious communications had been received and called to the attention of the department. During the three months which followed no less than six complaints were filed, all of them alleging the receipt of veiled threats, and neither the local authorities nor the men from Washington could find a single nail on which to hang a theory. Finally affairs reached such a stage that the chief sent for Allison, who had already made something of a name for himself, and told him to get on the job.