"I dare say that's the press at work," said Warrender in a whisper, after they had listened for a few minutes.
"Doing overtime," said Armstrong. "I suppose, not knowing exactly when Mr. Pratt will return, they want to make the most of their opportunity. Who knows how many thousands of pounds of spurious money are getting into circulation? No doubt Gradoff had his trunk full of notes that morning we saw him driving off in the car."
They seated themselves on the unopened bales, hoping that work would presently cease, and the man would leave the tower. But the thuds continued with monotonous regularity.
"Every thud means a forged note," said Armstrong. "They may be going on all night. How long can you stick it?"
"We'll wait till eleven; then if they're still at it, we'll go back and reconnoitre the outside."
"Perhaps they have a sentry."
"Perhaps; but I fancy they'll feel pretty safe now that they've chevied us from the island."
At eleven o'clock the work was still going on. The boys retraced their course to the ruins, regained the pram, and allowed it to drift on the current down channel to the south of the island. There they lay to for a few minutes, listening, peering through the darkness. There was no moon; the starlight scarcely revealed the outlines of the trees. Presently, with careful, soundless movements of the sculls, they rowed across to the left bank, and, pulling the craft out of sight, landed a little below the island, and laboriously pushed their way through the thicket, guiding themselves by the compass. Some fifty yards from the bank the vegetation thinned, and they found themselves in a wood of taller trees. Here the going was easier, though once or twice they stumbled over trunks that had been felled and stripped ready for carting. Emerging from the wood into park-like ground, where there were large trees only at intervals, they progressed still more rapidly, and at last caught sight, on their left, of the dim, square shape of the tower. Behind a broad elm they stood for a minute or two, watching. There was no light in the tower. Its base was surrounded by a mass of low-growing shrubs. The doorway, no doubt, was on the farther side from them. The walls were covered with ivy, except at the window openings, where the recent boarding was visible as faint grey patches.
"Now for it," whispered Warrender.
They stole forward over the long grass. As they drew nearer to the tower they heard the dull regular thudding; there was no other sound. Armstrong posted himself at one corner, while Warrender gently pushed a way through the shrubs to the wall. He examined the boarded window, apparently an old embrasure much widened. The boards were on the inside; the outside was protected by cross bars of iron. He went round the building. There was only one other window opening on the ground floor. At the north-eastern angle he halted, looking out for a possible sentry, then crept along until he reached the entrance, a low iron-studded door flush with the wall. Putting his ear against the wood, he heard more clearly the metallic thuds, and men's voices. A footstep approached. He slipped back to the corner, and crouched in the shelter of a shrub. The door opened outwards, creaking on its hinges, and letting out a stream of light. A short, stout figure emerged from the tower, carrying a number of cans which rattled as he walked.