As night fell the two officers prepared to renew their task. If Smith's surmise were correct, the actual business of breaking out of their cell seemed a fairly simple matter. Seton wondered why he had not thought of a similar plan before. Then he reflected that, had he done so, and had the work of getting clear of the Mole been successful, he would most certainly have attempted to make for the open sea. The idea of bluffing the Hun by going inland and thence across the Dutch frontier had never occurred to him.
Nevertheless the whole business was fraught with peril. The men were liable to be shot at sight by the sentries; if recaptured they might also be executed as spies, since they were not in uniform. Without doubt Count Otto von Brockdorff-Giespert would not be backward in taking any steps to make it decidedly unpleasant for them should they have the ill-luck to be recaptured.
Directly the rounds had made their usual inspection and had taken their departure, Alec and his R.A.F. comrade set to work. With only a marline-spike and two pairs of hands, the task of removing the cemented-in stone was a tedious and formidable one. They had to proceed cautiously and silently, lest the alert sentries detected the grating of cold steel against hard cement.
At intervals they desisted to listen. It was quite possible that the communication-tunnel might still be in use, in which case it was falling out of the frying-pan into the fire with a vengeance, and at the expense of a terrific amount of hard and purposeless toil.
"Wonder how goes the time," gasped Smith, pausing to straighten his aching back and to wipe the perspiration from his forehead. "Getting on for midnight, I should say."
"No fear; it's not much past eight o'clock," replied Alec. "I'll just see."
He went to the seaward aperture and gazed skywards. The night was dark and calm. The stars shone brilliantly, although obscured here and there by patches of mist. In the northern sky the Great Bear flamed in stellar splendour. By its position with relation to the Pole Star, Alec was able to confirm his surmise with a fair degree of accuracy.
"It's certainly not nine yet," he reported. "We've eight hours of darkness; ought to do something in that time. By Jove, this cement's hard! Wonder if it came from England?"
He took the marline-spike from his companion. It was wet and sticky. The pilot's hands, hitherto well kept and unused to hard manual labour, were almost raw. Alec's were not much better, while every muscle in his body and limbs was aching with the unwonted exertion.
Yet doggedly they continued their work, each man relieving the other at, roughly, a quarter of an hour's interval. The stone was beginning to show signs of working loose.