It was Polmore. The secretary was out of breath. He stared as he saw the guns that Whitburn and Stephen were holding. Whitburn put a querulous question.
“Well?” demanded the professor. “Where is Bragg?”
“Gone, sir,” returned Polmore. “I looked upstairs for him, after I called Bragg. He was not there. I went down to the dock. No sign of Bragg. He is gone.”
“How do you know that?”
“The little motor boat was missing, sir.”
Professor Whitburn bristled. He stared at Stephen, who solemnly shook his head. Then he turned to Polmore. The secretary was ready with his answer before Whitburn put the question that was in his mind.
“Bragg said nothing about leaving, sir,” declared Polmore. “If he had asked for the night off, I would have told you.”
“That is the rule,” declared Whitburn. “No one has the right to leave this island without my permission.”
“I always ask Mr. Polmore,” put in Stephen, “and wait until he tells me that I have your permission, professor. Bragg always did the same—”
“Not to-night,” interposed Polmore.
“That is evident,” stated Whitburn, testily. “Well, there is one way to call Bragg to task. He keeps his car at the little garage in Marrinack. I shall call there and find out when he left. Pick up a revolver, Polmore.”
While the secretary was obeying the order, Professor Whitburn thrust his automatic in a pocket of his smoking jacket. Stepping to the desk, the old man picked up the tilted telephone. He clicked the hook. The line was dead.
“Out of order,” fumed the professor.
“Maybe some one has tampered with the line,” suggested Stephen, in an anxious tone.
“It has been out of order before,” declared Polmore. “Always temporarily. Perhaps, professor, it is merely an interrupted service.”
“Probably,” agreed Whitburn, in a dry tone. “Nevertheless, the coincidence is unfortunate. Gentlemen” — he paused to hang up the receiver and draw his automatic from his pocket — “we are confronted by a most dangerous situation!
“Inasmuch as I can trust you both, I shall explain the menace that confronts us. I thought that I could trust Bragg also. His disobedience of rules, however, may mean that he is a traitor. If so, the danger is increased.
“Some time ago” — Whitburn stared steadily toward the door as he spoke — “I discussed plans for a new submarine with Commander Joseph Dadren, a retired officer of the United States Navy. The commander was working on a tremendous invention: a submarine that would travel by almost automatic propulsion.
“As you know, I was engaged — a few years ago — in the development of torpedoes that moved by chemical action.[1] Commander Dadren has been seeking to accomplish the same result on a larger scale. He studied the principles that I had used with my torpedoes. He began where I had left off.”
THE professor paused to shake his shaggy head. The gesture was one that indicated admiration for Commander Dadren’s remarkable genius.
“The submarine,” declared the old inventor, “has proven a success, despite my predictions to the contrary. Commander Dadren evolved new principles that aided him in his constructive effort. Nevertheless, he felt that he owed much to me; for my inventions had given him the inspiration.
“Not only that; he seemed to desire my opinion on the results he achieved. Therefore, he sent me a complete set of his plans. I am the only man — except the commander himself — who has seen those diagrams.
“I have kept the plans here in my study. I took pains to conceal them, knowing their importance. Should they fall into the hands of schemers, those plans could be sold to some government other than the United States.
“To-night, I discovered that an intruder had been searching through this room. Fortunately, the plans were untouched. At the same time, the fact that a search was made is proof that enemies are close at hand. When stealth fails, attack follows. That is something that I have learned through experience.
“We may, this very night, find invaders on this island. That is why I expect you to aid me in repelling any foe. I can sense the imminence of an attack. Therefore, I intend to make an inspection of this house before it comes.
“Remain here, both of you, until I return. Stay on guard, with revolvers ready. I shall be gone but a short while. I wish to take advantage of the time that still remains to us.”
With this admonition, the professor clutched his automatic and stalked from the room, closing the door behind him.
Stephen stood stolid. Polmore was nervous. The cat on the window sill, however, was no longer perturbed. It curled among the papers and sleepily closed its eyes.
OUTSIDE the study, Professor Whitburn walked hastily through the corridor until he reached a large central room where a clock was ticking loudly on a mantelpiece. The professor turned and went to the side door that opened to the path toward the dock. He made sure that the door was latched.
Moving to a flight of stairs, the professor ascended. He reached the second floor, then approached a locked door. Drawing a key from his pocket, the professor opened the barrier and went up a curving flight of stairs. He reached the old secluded tower.
This portion of the house formed a single room. It was almost pitch-dark; only a vague touch of clouded moonlight came from a skylight at the top.
In the corners of the room were large machines, covered with white cloths. These were devices for the projection of aerial torpedoes. The professor had experimented with them a few years before. Partly dismantled, the machines were no longer used.
There was a table in the center of the room. Groping through the darkness, the professor turned on a tiny light. He used this to find a pair of earphones and a mouthpiece. He made attachments that put a short-wave radio into operation.
Clicks sounded by the little light. A few minutes passed. Then came a response.
The professor began to dispatch in a code of his own. He paused to hear the answer. Then he resumed his sending. Although telephonic communication had been severed between Death Island and the mainland, Professor Whitburn had made contact with some one in the outside world.
The coded conversation continued. Sending and reception were terse. The professor signed off abruptly. He replaced the earphones and turned out the light. His chuckle sounded in the darkness. With surprising agility, the old man scrambled up on the table.
Stretching his bent form, Professor Whitburn managed to reach the skylight. He loosened a clamp and pressed upward. Rusty hinges groaned; then came a puff of night air through the opening. The professor tightened the clamp; bent downward and reached the floor. Softly, he went down the tower stairs and closed the door behind him.
The professor had noted the time of the clock in the lower room. He glanced at his watch in the dim light of the second-story hall. His trip to the tower had taken less than fifteen minutes. Again, the professor chuckled.
Prowlers — the disturbed study — the dead telephone line: these troubled him no longer. By means of the short-wave set, he had countered the thrust of impending danger. Time was the only factor that remained to be met.
Professor Whitburn had established radio communication with a man named Burbank, a person whom he had never seen. Yet he had followed Burbank’s instructions to the letter. The opened skylight; the unlocked door to the tower — both suited Burbank’s request.
New confidence gripped Professor Whitburn. Through the old man’s mind crept memories of the past — when other danger had confronted him. He had been saved in that past by the intervention of a powerful friend known as The Shadow. It was on The Shadow that the professor depended in this present crisis.