"That, Miss Norton," explained Whitney, "is the point of your story that makes the whole thing look rather suspicious. I will confess that when the chief told me what you had said over the phone I didn't place much faith in it. There might have been a thousand good reasons for men allowing a local taxi to wait at the corner, but the very fact of its bearing a New York number makes it a distinctly interesting incident." "Then you think that it may be a clue, after all?" "It's a clue, all right," replied the operative, "but what it's a clue to I can't say until we dig farther into the matter. It is probable that these two men had a date for a poker party or some kind of celebration, missed the train in New York, and took a taxi over rather than be left out of the party. But at the same time it's distinctly within the realms of possibility that the men you saw were implicated in last night's explosion. It'll take some time to get at the truth of the matter and, meanwhile, might I ask you to keep this information to yourself?" "Indeed I shall!" was the reply. "I won't tell a soul, honestly." After that promise, Al left the Norton house and made his way across town to where the munitions factory reared its hastily constructed head against the sky. Row after row of flimsy buildings, roofed with tar paper and giving no outward evidence of their sinister mission in life--save for the high barbed-wire fence that inclosed them--formed the entire plant, for there shells were not made, but loaded, and the majority of the operations were by hand. When halted at the gate, Whitney found that even his badge was of no use in securing entrance. Evidently made cautious by the events of the preceding night, the guard refused to admit anyone, and even hesitated about taking Al's card to the superintendent. The initials "U. S. S. S." finally secured him admittance and such information as was available. This, however, consisted only of the fact that some one had cut the barbed wire at an unguarded point and had placed a charge of explosive close to one of the large buildings. The one selected was used principally as a storehouse. Otherwise, as the superintendent indicated by an expressive wave of his hand, "it would have been good night to the whole place." "Evidently they didn't use a very heavy charge," he continued, "relying upon the subsequent explosions from the shells inside to do the damage. If they'd hit upon any other building there'd be nothing but a hole in the ground now. As it is, the damage won't run over a few thousand dollars." "Were the papers right in reporting that you picked some fragments of a black bag not far from the scene of the explosion?" Whitney asked. "Yes, here they are," and the superintendent produced three pieces of leather from a drawer in his desk. "Two pieces of the top and what is evidently a piece of the side." Whitney laid them on the desk and examined them carefully for a few moments. Then: