After his disquieting interview with Miss Fitzgerald, Stanley felt the imperative need of an entire change of subject to steady his mind. This want, the secret of the old tower supplied.

No time could have been better suited for his investigations. Lunch was well over, the members of the house party were in their various rooms for an hour at least.

A few moments spent in measuring on the first floor in the great hall, and the library, which ran parallel to it, proved the correctness of his theory, that the space enclosed was smaller at the bottom than at the top, as only six feet was unaccounted for. Evidently on this floor the tower contained merely a staircase.

He now carried his investigations to the second storey. The room over the library had been assigned to Kent-Lauriston, and as the Secretary's knock elicited no answer, he took the liberty of entering, finding, as he supposed, that his friend had gone out. The inside measurements of this room gave only ten feet, where they should have given twenty-five, and brought up at a large fireplace, which had no existence in the apartment below, and which was apparently much deeper than was really the case. Around and behind this there was a secret chamber of considerable dimensions, but half an hour's experiments brought the Secretary no nearer effecting an entrance. The old blue glazed tiles of the fireplace, and the bricks which composed its floor, were alike immovable. There was only the roof left; if he failed there, he must resign himself to the inevitable, and bend all his energies on trying to open the secret door.

At the risk of being thought prying and meddlesome, Stanley now proceeded to search for some mode of ascent to the leads, and after many mistakes and much wandering, he discovered at last a worm-eaten ladder. This he climbed, at great bodily risk, and forcing a rusty scuttle, emerged at last, safe and unperceived, on top of the house, amidst a wilderness of peaks and undulations, which attested more to the ingenuity of mediæval builders, than gave promise of comfort to him who attempted to traverse it. At last, however, by dint of much scrambling, and several hair-breadth escapes from an undignified descent to the lawn, he reached the point at which the tower sprang from the roof. It rose sheer above him for almost forty feet, unbroken by any window or excrescence, and thinly covered by ivy which, while it was too scattered to conceal any outlet, at the same time afforded no foothold for ascent.

It was dreadfully tantalising. Once on those crumbling battlements, he persuaded himself he should have no trouble in entering through the roof. The missing letter was then within reach, and the young man saw the road to rapid promotion stretch glitteringly before him; saw that Darcy would be in his power, with all that it implied; but saw that forty feet of frowning masonry, which separated him from his hopes, and cursed his luck.

A ladder would solve the problem – but for numerous reasons it was a solution not to be thought of. Above all things, he wished his investigations to be absolutely unsuspected. If Darcy for an instant imagined that the truth was known, he would be off like a flash. If the Secretary was to conquer the secret of the tower, he must do it unaided, and he was about to turn back and descend, baffled by the hopelessly smooth surface of the structure, when his eye caught sight of a small iron ring in the side of the tower, about two feet above the roof of the house. Examining closely, he saw a second ring two feet above the first, and others at like distances up, presumably to the top, though the ivy had in some cases concealed them. His first conjecture was that at some time there might have been a rope ladder arranged; but that would have called for pairs of rings at the same level, and the closest scrutiny failed to reveal more than one.

Perhaps, thought Stanley, it might be possible to rig some sort of a contrivance of rope to these, by means of which he might ascend; but it was difficult to procure the necessary material, and still more difficult to attach it to the tower without attracting observation. He caught hold of the ring and gave it a good jerk towards him to be sure it was firmly enough embedded to be of some service, when, to his utter astonishment, not the staple, but the block of stone to which it was attached, pulled out about six inches. Here was an unexpected dénouement. If the masonry was as rotten as all this, it was high time, for the safety of the house, that it was pulled down. A moment's examination, however, assured him that the tower was as solid as a rock. Why then should this one stone be loose, and why could he pull it no farther? He pushed it in again and pulled once more with all his strength, but it came only the six inches, and then remained immovable. He bent down and examined it closely. Then, as he perceived there was no trace of mortar on its edges, he gave a shout of exultation, and seizing the second ring, drew it towards him with a similar result. The stone to which it was attached pulled slightly out. Unwittingly, he had stumbled on to one secret of the tower. These stones formed nothing more or less than a concealed staircase; perilous indeed, but quite possible of ascent. Springing up on the first and second stones, he found they bore his weight, and he was thus enabled not only to steady himself by the rings above, but to pull them out in like manner. Having tested three or four and pulled out six, he descended again to the roof, and returned to his room to provide himself with certain necessaries for the trip, among which were a small bicycle lamp and a match-box. He took off his coat and waistcoat, and also his shoes, and set about making the attempt in a more practical manner. For at least half the way up he would be screened from view by the roofs, and for the remainder he must take his chance of not being seen. Drawing a long breath, and placing his foot firmly on the first stone, he commenced the ascent. For ten or fifteen feet it seemed an easy matter, but as he cleared the intercepting roof peaks, and the view opened out, he fully realised his perilous position, and a gust of wind which swayed him on his airy perch made him feel all the more insecure. Sternly resisting the temptation to look down, and the no less dangerous desire to hasten his ascent, he kept his face resolutely turned to the wall, and testing carefully each ring before trusting himself to it, climbed slowly up and up. The way seemed endless, and when but six feet remained, two sparrows, with a whir and rush of wings, flew angrily round his head, at what they regarded as an invasion of their nest, and almost caused him to lose his hold in an attempt to drive them away. And now the battlements were just over him, projecting awkwardly from the face of the wall, and proving much higher than he had at first supposed. But he noticed, with relief, that directly in the line of his ascent were a pair of projecting iron stanchions not visible from below, but evidently intended to be used in pulling oneself up and over the battlements; a supposition borne out by the fact that they were placed each side of a break in the stonework, which was ornamented with a lip or step of smooth stone, evidently intended to afford an entrance to the roof of the tower. This lip had a slight slant upwards, and might perhaps have served a double purpose as a drain or broad spout.

Fortunately Stanley's caution had not entirely deserted him, and he had the good sense to reach up and test one of the stanchions before trusting himself to it. It was well that he did so, for its fastenings proved to be rotten with age, and the bolt giving way, it tore out in his grasp, and flying from his hand fell with a loud clank on the roof, forty feet below. The Secretary swayed out from the tower with the force of the shock, and had not the topmost iron, to which he clung, held firm, this narrative would have come to a sudden and a tragic ending.

Having recovered his equipoise, he found himself face to face with a serious if not an insurmountable obstacle. The natural entrance to the roof was denied him; for even if the other stanchion held firm, he had no mind to trust his entire weight to it, and without its mate it was of little use for lifting himself up. Besides which, the lip or step, which, by its slant towards him, would, with the aid of the stanchions, have made access easy without them, rendered it, by reason of its angle, the more difficult. The only practical way seemed to lean far to one side, and seizing the rough stones of the battlement which projected over his head, swing himself up and through one of the embrasures. The last step would bring him breast high with them, but as they projected nearly a foot beyond the face of the tower, he must bend his body outward, and trust to them alone for support. If the stones of the battlements were strong, his athletic training gave him no reason to suppose that he would have any trouble in accomplishing the feat. Youth, moreover, is apt to be venturous, and an aerial perch, eighty feet from the ground, is not just the place one would choose for lengthy consideration.

Therefore, after reaching up and testing the masonry, as thoroughly as he was able, he flung caution to the winds, a full assemblage of which were whistling around him, and, making a desperate effort, clutched the stones above him, and swung his body up and one leg over the battlements.

He was secure after all. Then, looking within, he received one of the worst shocks which the events of his life had ever afforded him. There was no roof in existence; at least, none where he had expected to find it. He discovered that he was seated astride the rim of a circular well, forty feet deep, whose bottom was the roof of the house. In other words, the whole tower above the second story was a shell – a sham. A few moments' observation was sufficient to assure him that there never had been a roof at a higher level. An iron bar corroded with rust, round which was wound a chain, stretched across the diameter of the well, and had evidently furnished at one time support for a flag-staff, to further keep up to the outside world the deception of a roof; but otherwise the inside was perfectly smooth, even the holes where the steps were pulled out not showing, which bore evidence to the fact that they worked in the thickness of the wall.

Down at the level of the roof two or three little beams of light marked the location of certain gargoyles or antique water-spouts, which Stanley had noticed on the outside, and marvelled that they should have been placed in the middle instead of the top of the tower. These explained the absence of water in the well.

Looking down, as his eyes became accustomed to the gloom, he was able to see something of the nature of the roof, which must enclose the secret chamber. It was covered with dust and debris, but he was positive he could distinguish certain little bumps or lumps, which he shrewdly guessed to be thick diamond panes of glass, set in lead, and which, as he conjectured, furnished light to the room beneath. Entrance to this apartment seemed totally lacking from the roof, or else concealed by the dust of centuries. No staircase could he discover on the inside of the well, and he was about to relegate it to the limbo of unfathomable mystery, when a startling discovery gave him the key to the whole matter. It was, he saw, manifestly impossible to go down inside without falling, after which, if not killed by the shock, he would be left to starve at his leisure, while his friends searched the country-side for him. But if to descend within was impossible, to descend without presented almost as many difficulties. To go over the battlements as he had come, was well-nigh hopeless; but if he could walk along their inner rim for a foot or two, round the next embrasure, to the natural slanting entrance which was directly over the first step, the descent would be, comparatively speaking, easy. To rise from his present posture and assume a standing position on the twelve-inch rim of a structure eighty feet in the air requires a steady head, and though the Secretary was possessed of this, he did not at all relish the undertaking. It had to be done, however; but after his previous experience he determined to take no more risks, and reaching out from his position of vantage, he tested carefully every step of the way. At last only the slanting step remained. Reaching far over he touched it with his hand, when, to his horror, it practically revolved, now pointing down into the interior of the tower, its outward end pointing up. He shuddered when he saw the fate which the fortunate accident to the stanchion had caused him to escape. Had he descended in the regular way and stepped upon the slanting plate, the instant his foot passed its centre of equilibrium, it would have revolved, and without a doubt flung him down into the interior of the well. It was a cursed, mediæval trick, a fitting accompaniment to the inquisitorial horrors of those ages – an English oubliette. If the fall did not finish the daring invader of the tower – the inhabitants of the secret chamber doubtless had means to insure his end, or perhaps he was merely left to starve.

Touching the plate once more he pushed it back to its original position, and found that it remained stationary. As long as he kept on the outward side he was safe, and if the Secretary observed this rule he could easily avail himself of the plate to descend by, for the perpetrators of the villainous arrangement had evidently not thought it necessary to make it entirely revolve, as one who had once gone up the tower was never expected to come down the outside again. And now, with great caution, he wormed his way to the treacherous step, and with still greater care placed his foot on its outer edge; it held firm, and he ventured to plant both his feet upon it. But, alas! he has forgotten how slippery a flag of slate, polished by two hundred years' exposure to the elements, may become. His feet slipped from under him, and in striving to save himself he overbalanced the stone. Instantly it revolved, and a second later he found himself suspended over the well, with only the strength of a despairing grasp on the edges of the slate between him and eternity.

CHAPTER XXXIII
THE SECRET OF THE DOOR

Miss Fitzgerald's disclosures to the Marchioness, as it turned out, rather helped than hindered those principally concerned, for Mr. Lambert met her Ladyship at the church, and his explanations took the keen edge off the wrath which she vented on her daughter a little later, and in the midst of which Lieutenant Kingsland arrived, with ample assurances of worldly prosperity, which overcame her strongest objections, and went far to reconcile her to the inevitable. Her disappointment, however, was keen, and her temper suffered in consequence, so that dinner, at which the Secretary's unaccountable absence formed the chief topic of conversation, was distinctly not a success, and the ladies retired early, leaving the gentlemen to their own devices.

Miss Fitzgerald claimed to join in the general hegira, but her actions belied her words, for shortly after she was supposed to have gone to her room, her figure, its white dinner dress concealed by a long grey cloak, might have been seen gliding across the lawn in the direction of the inn.

The night was pregnant with great events, though outwardly calm and beautiful, and the great hall in which Mr. Riddle, Kent-Lauriston, and the Lieutenant stood smoking, after having been dismissed from the drawing-room, was flooded with moonlight.

"I say," remarked Kingsland irrelevantly, after a long interval broken only by the conscientious puffing of cigarettes, "how that mediæval prize puzzle shows up in the moonlight."

"The secret door?" asked Kent-Lauriston. "Yes, it does. I heard the butler making his plaint about it yesterday. It appears it's no joke to keep those nails polished."

"I shouldn't think it would be, and I dare say the bulk of the servants wouldn't touch it with a ten-foot pole. I wonder what's behind it, anyway."

Nobody said anything.

"I wonder if Darcy'll ever get his letter?" asked Kent-Lauriston, glancing at Mr. Riddle. "Anyway, it's as safe behind that portal as if it was in the Bank of England. Safer, in fact, for he can't get it out if he wants to."

"I don't think there's much chance of anyone's opening it," said Mr. Riddle. "Cleverer men than Colonel Darcy have tried to solve that problem in the last two centuries, and failed. I imagine, however, if it ever does come to be opened, that a certain theory will be proved correct."

"What is it?" asked Kingsland.

"That the prophecy tells only half the story. To press the nails they must be flexible, but they're firm and immovable."

"Well?"

"Well, it's evident that there is some catch or spring to be worked first."

"How do you make that out?"

"These five nails we hear so much about are really the key to the lock, but until the movable impediments – or, to give them their technical name, the 'tumblers' – are so arranged as to release the key, the lock cannot be opened."

"It's a rum sort of key, with no keyhole," said Kingsland.

"The key to open this lock is a mental one, rather than one of steel and iron. In other words, a puzzle lock like this always has certain movable parts, the movement of which constitutes the enigma."

"Ever heard of any locks like this one?"

"Not exactly, but the Russians, Hindoos and the Chinese have their puzzle locks in the shape of birds or animals, and they're locked or unlocked by pressing certain parts of their bodies. You can depend on it, some spring must be worked first, which relieves the nails from their tension and permits one to work the combination."

"But no such catch or spring is visible."

"Of course not. It would be the most carefully concealed of all the mechanism; but some lucky fellow will stumble on it eventually, and if he has presence of mind enough to press the nails also – Presto! your door will fly open."

"And what will he find?" asked Kent-Lauriston.

"From present appearances," replied Mr. Riddle, "a little pile of dust, which some centuries before was a letter – "

"I shouldn't be satisfied with anything less than a mouldering skeleton in chains," said Kingsland.

"Or a complicated astrological machine, such as one hears about in Bulwer's grewsome ghost story," added Kent-Lauriston.

"The inhabitants of this house are too unfeignedly easy-going and comfortable to admit of such a supposition," replied Kingsland, and turning to Kent-Lauriston, added: "What do you think is inside the Tower?"

"I don't know, and if I did, I shouldn't tell anyone."

"Why not?"

"Because if its contents are so unpleasant, that they had to shut it up for ever, it certainly wouldn't prove a fit subject for conversation."

"Well, anyhow," said the Lieutenant, "I trust the discoverer will be a short man, or he'll hit his head a nasty crack, when he tries to go in."

"Wrong again," said Mr. Riddle. "I think you'll admit that I'm medium height for a man; but if I stood with my back to the door, my head wouldn't hit the top of the arch."

"Nonsense. Let's see."

Riddle took up the position indicated, facing them.

"You're right!" ejaculated the young officer.

"I'm amazed! I supposed it was much lower. What do you measure?"

"Five feet eight inches. But it is the extreme width of the portal which makes it deceptive; it lowers it. I think, if I stretched out my arms, straight from the shoulder, I should no more than touch the side – see – " and he made a great cross of himself, against the black oak.

"What are you fumbling at?" asked Kingsland sharply.

"My fingers hardly touch – it's a stretch. Ah! now they do."

"You look ghastly in the moonlight; put your arms down and come away."

"I'm very comfortable here, barring my back; those silver nails are rather sharp," and he put his hands behind him.

"Come away," said Kingsland, nervously, seeing something in his face he did not like. "You look as if you'd been walled up a few months ago, by some inquisition, and we'd just unearthed you in your niche."

"By heavens! some of these nails are loose!" cried Riddle.

"Nonsense!" retorted Kingsland. "You've thought so much about it, you'd imagine anything. They're as firm as – well, nails. I tried them myself. That door won't be opened in our lifetime, unless – " but the Lieutenant never finished his sentence, for he had paused suddenly, in open-mouthed astonishment. Without warning, and without a sound, the portal, closed for centuries, swung slowly inward, carrying Riddle with it; who, catching in vain at the sides of the door in an attempt to save himself, fell heavily backwards down three steps into the secret chamber.

Seeing that he did not immediately rise, but turned over partially on his side, Kingsland recollecting himself, sprang forward to his aid, crying:

"Have you hurt yourself?"

"No, no," he replied, waving him off, and slowly rising from the floor, covered with dust.

"By Jove!" exclaimed the Lieutenant. "How did you ever do it?"

"Don't know, I'm sure," replied Riddle, emerging from the portal, and vigorously brushing himself. "As I told you, the nails, or some of them, felt loose – I pushed them, and the next thing I knew the door revolved and I was on the floor."

"You're a genius!" exclaimed Kingsland. "But," peering down into the darkness of the tower, "where's Darcy's letter?"

"We need a little light on the subject," said Mr. Riddle. Stepping to the fireplace, he lighted an old wrought-iron sconce, full of candles, which stood on the broad mantelshelf, and approached the secret door.

In the light of the candles, all could see that, except for the little space into which he had fallen, the whole interior of the tower was filled by a narrow stone staircase, which, in its ascent, half turned upon itself. Of the missing document, however, there was not a trace. The stillness in the great hall was oppressive. Even their own footsteps on the stones seemed, to the hearers, preternaturally loud.

Mr. Riddle raised the sconce above his head, and there burst on a sudden a shimmering flash of a thousand prismatic colours from the head of the staircase. He fell back a step, as did the others, and Kingsland murmured in awe-struck tones: —

"What's that?"

Riddle again raised the sconce, and again the burst of light from the head of the stairs overwhelmed him, but this time he stood his ground.

"What is it?" asked Kent-Lauriston.

"I don't know."

"Let us examine."

"As far as I can make out, it's a flexible curtain of chain mail – hung across the staircase."

"I swear it moved," said the Lieutenant.

"No, it was the light which moved," replied the discoverer. "You see," and he swayed the sconce from side to side, making the curtain appear to be moving silently.

"If I take the light away," he continued, "there's nothing to be seen;" and he removed the sconce, leaving only the black mass of the steel curtain visible.

"Nothing to be seen – isn't there? Look there!" whispered Kingsland, and, following the direction of his eyes, the others saw a broad band of blood-red light steal out of the blackness, across the steps at the head of the staircase.

"That room has been closed for centuries, and yet there is a light burning," he continued hoarsely. "Shut the door, my dear fellow, and let's get away."

"It merely confirms another theory of mine," said Riddle, "which is, that, as there are no windows on the outside of the tower, they must have got their light and ventilation from the roof. I think it's fair to suppose that they used red glass, and that the full moon is shining through it."

"Then you can go and prove it if you like, but if you take my advice, you'd better leave it alone."

"I don't like, my dear Kingsland, though I'm going, just the same. I daresay I shall find something very nasty at the head of the stairs, but it won't be supernatural. If I want you, I'll call you. If not, wait till I come back." Putting down the sconce, he slipped off his dress coat, and crossing the hall, picked up a stout hunting crop, the property of the Lieutenant, while his two companions stood staring at the blood-red band of light which lay across the steps, and which seemed to their excited imagination to grow broader and deeper.

"What do you think he'll find up there?" asked Kingsland.

Kent-Lauriston shrugged his shoulders.

"I don't wish to think," he replied. "But I'm certain that, to this very day, there lie hidden away in some of our old country houses the ghastliest secrets of mediæval times, the fruit of crimes and passions, of which, happily, even the names have perished."

"What's that?" said the young officer, laying his hand on his companion's arm, and in the silence both distinctly heard the click of a latch, and facing round at the same moment, confronted the white face of Colonel Darcy, framed in the hall door.

In an instant he was at their side, drawing a quick hissing breath and exclaiming: —

"It's open. Where's my letter?"

"There is no letter," said Kingsland gruffly. "But you gave us a jolly good start, creeping in. This ghost business sets one's nerves all on edge."

"Who opened the door?"

"I did," said Mr. Riddle, coming up just at that moment.

"Ah! Then you have my letter."

"No, I haven't seen a trace of it. It may be up aloft."

"I believe there's some living object up aloft," said Kingsland. "If you take my advice, you'll shut the door, and leave it and the letter in perpetual seclusion."

"I don't care whether it's a man or a devil!" cried Darcy, who, whatever else may be said of him, did not know the meaning of fear. And as he spoke, he set one foot upon the lower step.

"Hold on!" cried Kent-Lauriston. "There's something up there, and, what's more, it's coming down." And as he spoke, a sound was heard in the long closed chamber, and as the listeners held their breath, something slowly approached the steel curtain, which swung out noiselessly as if waving in a ghostly wind.