But ring it did on this occasion, and over the wire came this ominous message: “Look out for yourself, Tom Swift! We’ll get you yet!” CHAPTER XIV THE AIRLINE EXPRESS Like a flash Tom Swift realized that this warning had come from those daring enemies of his who were still at large—the same men, Kenny and Schlump and the two masked ones, who had kidnapped him. He could realize their rage at his escape, their anger at the foiling of their plot to blow the place up by bombs, or, if their intention was not to cause serious damage, but only confusion, during which they might rob—this, too, had been frustrated. For a moment the sinister character of all that had taken place stunned the young inventor. The danger under which he was, came to him with a sickening realization and he sat for a moment holding the receiver in his nerveless hand. He was brought back to a sense of realities by hearing the somewhat distant voice of the operator asking: “What number, please?” That stirred Tom into action. “Look here!” he cried into the instrument. “You don’t realize how important this is! I’ve received a threat over the wire! I must trace——” “Hold the line,” interrupted the girl in a matter-of-fact tone, and, for a moment, Tom felt hopeful that he could thus get on the trail of those who sought to injure him. But while he was even thus hoping another voice broke in on his thoughts saying: “This is the manager, have you any complaint to make?” “Oh—no!” exclaimed Tom in despair, realizing how useless it was to try to trace the call thus. He was going through much the same experience Ned had gone through the time Tom called him from the farmhouse and then fainted. “I’ll call and explain. This is Tom Swift speaking,” he told the manager. “I want to trace a call that came over my private wire, but I can do it best by a personal visit, I believe.” “We will do all we can for you,” the manager said, for she knew the Swift concern was a large and important one. “It is often difficult to trace stray calls that may be made from any of a hundred pay stations. But I will help you all I can.” “Thank you,” said Tom, and hung up the receiver. Then he fell into deep thought. As he had feared, the danger was not over. His enemies were only biding their time. They had failed in their first efforts, but they were not going to give up. The sinister threat was enough to disclose that.