But Von Lertz did not know, and continued to enlarge upon the efficacy of the precautions which had been taken, and how impossible it was for the Secret Service to have learned anything of the present plot. As he was talking a knock came on the door and a bellboy, the same one who had taken Dixie's piece of string from the floor of the corridor, put his head in: "Did you ring, sir?" he asked, "No, sir? I am sorry." The door was closed but a message had been delivered. To Dixie Mason the appearance of the bellboy at the door meant that her bit of string had reached Grant and had been understood. On the string she had tied knots spaced to the dots and dashes of the Morse code spelling out the following message: "Lock fourteen. Ten o'clock. Watch alley." "In a moment Jacobson will be starting," said Von Lertz moving toward the window. Dixie accepted his unspoken invitation and moved to his side at the window and gazed down into the rapidly darkening alley. A moment after she had taken her position a figure emerged onto the fire escape, and it did not take the whispered words of the spy standing next to her to identify it as Jacobson. The dynamiter gathered up two large packages which were already on the platform outside his window and then made his way gingerly to the ground by way of the frail steel stairway. An automobile crept up to him out of the shadows of the building. Jacobson got in. The car began to move forward out of the alleyway and Dixie Mason became filled with a fearful dread. Suppose her message had not been understood and no watch had been placed on the alley? But, no. A figure suddenly launched itself from the kitchen loading platform onto the running board of the car. A second appeared from the garbage cans, and the glint of a revolver could be seen in his hand, as he vaulted into the vacant seat by the driver. The car came to a sudden halt and a terrific struggle ensued in the tonneau. The struggle was short lived however. A revolver shot, the flash of which showed it to be in the air, and Jacobson was a prisoner. "Look, look, isn't that Harrison Grant," gasped Von Lertz clutching Dixie's arm as another figure appeared in the alley running toward the car. "Anyone hurt here?" It was a call from the running figure which made his identification as the president of the Criminology Club a certainty. Von Lertz who had been cursing fervidly as he gazed into the alleyway suddenly, affrightedly, became aware of his own precarious position.