"Get on a pair, Madden," he advised. "Civilian trousers will be conspicuous in a bright light. You are going to see this thing through, aren't you?"

Madden nodded and followed his companion's example. Five minutes later the two, transformed into German sailors, walked out of the hanging laundry.

"Don't seem, to observe anything," whispered Caradoc. "Appear to be going somewhere, on an errand. Walk just as if you belonged aboard."

A moment later the Briton turned down a stairway that led to a shadowy deck, which was hung with long rows of hammocks with men sleeping in them. The air down here was remarkably cool, although Madden did not have time to give much thought to this. Caradoc pursued his way unhesitatingly among the sleeping sailors, and presently came to another hatchway, out of which poured the rumble of machinery and a stream of light.

Down this flight of steps, Smith moved with certainty, and a moment later Madden saw they were entering a great machine shop. A full complement of men worked at every lathe, table, drill or saw. The clang of hammers, the guttering of drills, the whine of steel planes smote his ears in a cheerful din of labor. The laborers worked at their tasks with that peculiar flexibility of forearms, wrists, fingers that mark skilled machinists. The scent of lubricating oil the faint tang of metal dust filled the air. Strange to say, the air down here was even cooler than that in the sleeping deck above.

All sorts of queer tasks were progressing. Here, men were working on gyroscopes that fitted into the shells of torpedoes; there, they fabricated little hot-air engines which propelled those instruments of destruction. They were repairing gauges, steam connections, electrical fittings, what not.

Madden was tempted to pause and stare about this wondershop, when it occurred to him that if he and Caradoc were discovered they would be executed as spies. He had not thought of this before, and the mere suggestion somehow made him feel stiff and wooden. He was not frightened, but he felt clumsy, as a schoolboy does when he makes his first public speech. His arms and legs felt wooden; his head did not seem to sit in a natural manner on his neck. He felt that if anyone glanced at him, he would immediately betray himself. His walk, his looks showed it. He could not imagine why some workman did not leap out, seize his arm and yell "Spy!"

After a long stage-frightened walk, Caradoc turned down another flight of stairs. Here Madden discovered the secret of the cool air. On this deck was a big refrigerating plant, with frost-covered pipes leading in all directions. The sight of this plant gave Madden some faint insight into the thorough preparation made by the German government to carry on their struggle by sea. Long before war was declared, Germany must have planned a naval base in the Sargasso, and have foreseen the use of her submarines in evading the blockade. She had chosen these untraveled seas as a depot, then established a refrigerated machine shop in order that the full-blooded German might work comfortably in the tropics. The plan seemed to have been worked out with infinite detail.

From the refrigeration deck, they descended to still another deck into the very bowels of the ship. This descent brought them to a long gallery that was formed by a bulkhead running down the center of the ship. As they entered this passage, three workmen came out of a small steel door that opened into this central wall. One of the workmen carefully rebolted the door, yawned sleepily and followed his comrades toward the companionway. As he passed he grunted something to Caradoc. Madden's heart beat faster lest they should be discovered at this last hour. He had no idea what mission moved the Englishman, but he sensed that here was his destination. Smith made some reply in German, moved briskly ahead until he came to the small steel door. He laid his hand familiarly upon the bolts, shot them back, swung open the door. One of the men whirled about and stared back at this assured intruder. Smith stood aside and with a curt military gesture motioned Madden to enter. The American drew an uncertain breath, glanced at the three Germans out of the tail of his eye and stepped into the dark square. Caradoc followed him. The laborers went on updeck apparently satisfied.

An electric wire was let in through the door. Caradoc reached for it, followed it with his hand and presently turned a switch. Next moment a bright flood of light bathed the tubular chamber in which they stood.