Suddenly a hand grasped Rollo's shoulder in a vice-like grip, and the muzzle of a revolver was clapped against his temple.
"One sound and you are dead!" exclaimed a stern voice.
The lad was already convinced that the so-called British army officers were Germans in disguise. Not only was he sure that the pseudo Major Duncan-Dean was an impostor; the peculiar phraseology of the man who had replied to the commandant's message confirmed his conclusions. To crown everything, there was the conviction carried by the muzzle of that revolver.
Rollo spent a nasty minute. His mind was working furiously, weighing up the factors of the situation. To raise the alarm meant death to himself; to fail to do so might result in the cold-blooded massacre of Commandant Fleurus and several of the staff; while, with the head-quarters telephone at their disposal, the four Germans might play havoc with the plans of the Belgian Commander-in-Chief.
The Germans were talking rapidly in a low tone. The one who held Rollo prisoner still kept the revolver against the lad's temple; the rest had each drawn an automatic pistol, and were evidently about to force their way into the presence of the commandant.
"I'll wait till those fellows go out into the corridor," thought the lad, "then I'll try the effect of a sudden blow in this gentleman's wind. It may do the trick; if not, my number's up. Anyway, it's better than being snuffed out without making an attempt to fight for it."
Although he kept as quiet as he possibly could, Rollo could feel his heart thumping violently, while his temples throbbed until the muzzle of the German's revolver seemed to be beating a tattoo.
"Keep steady!" hissed his captor. "This pistol has hair-trigger. Might go off if you shake."
It was on the tip of Rollo's tongue to reply that he was not shaking by reason of fear; but realizing that such a statement might put the German additionally upon his guard, the lad kept silent.
Presently one of the conspirators replaced his revolver, and with his free hand grasped the handle of the door. The other two stood behind, ready to sally forth on their murderous and treacherous work.