The Germans held, at that time, nearly two million prisoners of war, of which upwards of twenty thousand were officers; the men and non-commissioned officers--as Gerry had heard--were distributed in more than a hundred great camps, while for the officers there were about fifty prisons scattered all over the German states. These varied in character from sanatoria, newly erected high-school buildings, hotels, and vacated factories, to ancient brick and stone fortresses housing prisoners in their dark, damp casemates. The _offizier-gefangenenlager_ to which Gerry and his three companions finally were taken proved to be one of the old fortress castles just east of the Rhine, in the grand duchy of Hesse; its name was Villinstein, and it housed at that time about five hundred officers and officers’ servants. There Gerry and his three companions were welcomed, not alone for themselves, but for the news which they brought with them; and Gerry, being an aviator, found himself particularly welcome. “For a flyin’ man we’ve been a-waitin’, Gerry, dear,” Captain O’Malley--formerly of the Irish Fusiliers--whispered and all but chanted into Gerry’s ear soon after they became acquainted. All allied officer prisoners--as German official reports frequently complained--planned an escape; but some schemed more than others. And the heart, if not the soul, of the schemes of escape from Villinstein was the black-haired, dark-eyed, light-hearted Kerry man of twenty-four summers, who was back in the casemates with his fellows again after six weeks of “the solitary” in a dungeon as punishment for his last effort for liberty. “’Tis this way,” O’Malley initiated Gerry immediately into the order of those bound to break for freedom. They were standing alone at a corner of the castle, which gave view over the ground to the east. “Out there you see the first wire--’tis often charged with electricity at night--to catch us if we leap over these walls. Beyond you see the second entanglement of the same persuasion; after that--nothing at all! Do you see?” Gerry admitted vision, as though the walls below them, the guards and the two wire barriers were merest trifles. “We’ve been beyond many times,” the Irishman motioned, unfolding his theory of immateriality of the apparent obstacles. “Many times.” “How?” Gerry inquired. “By burrow, mostly. Now and then in other ways; but by tunnel is most certain. ’Tis harmless amusement for us, the enemy think; so they let us dig, though they know we’re doing it, till we’re ready to run out. Then they halt us and claim the reward. ’Tis arranged so.” Gerry nodded. He had heard long before, from escaped prisoners, that at certain camps the Germans made little attempt to prevent tunneling until the burrows were almost completed. The German system of rewards, by some peculiar psychology of the command, gave more credit to guards for “detecting” an escape than at first preventing it.