"Stay where you are, Watkins," I commanded. "Let me have that torch, Nikka."  
I turned it on the over-mantel. An efficient kit of burglar's tools reposed on the mantel-shelf under the carven group of dancing monks, ale-horns and tankards waving aloft. The figure in the middle of the group had a comically protruding belly that seemed to waggle as the light played on it. But what interested me was the small flexible saw that was still fixed in the base of the panel above the dancing monks.
 
"Do you see what our friends were up to?" I asked. "That fellow Toutou has a keen mind. He is somebody to be reckoned with. He saw what none of us saw, even after we had worked out the cipher."
 
"What did he see?" asked Nikka.
 
For answer I switched the light on to Lady Jane's verse:
 
Whenne thatte ye Pappist Churchmanne
    Woudde seke Hys Soul's contente
He tookened up ye Wysshinge Stone
    And trodde ye Prior's Vent.
 
 
"He saw that," I answered. "And he jumped to conclusions from it. He knew, as we knew, that there is something concealed in this house, probably in this room. And he thought that that verse would not have been placed just there unless there was a reason for it."
 
"By Jove, I believe he was right!" exclaimed Hugh.
 
Nikka propped a chair against the mantle-piece, and climbed on to the shelf. The panel had been sawed through on both sides and part of the bottom.
 
"Go ahead," said Hugh. "It's ruined anyway. But I swear I don't see how there can be an opening in back there that wouldn't sound hollow when you rap over it."
 
While I held the light on the panel Nikka sawed away, and in fifteen minutes he had it detached from its beveled frame.
 
"Come up here, Hugh, and help me with it," he said, as he withdrew the saw, and Hugh climbed to his side.
 
They found a thin chisel in the burglar's kit, and with this Hugh gently pried the panel loose.
 
"It has a stone backing," cried Nikka disappointedly, as it came away.
 
In fact, we all experienced a profound feeling of disillusionment when Watkins received the panel in his arms, and the empty area of stonework was revealed, about four feet long and three feet high.
 
"Too bad," said Hugh, jumping down. "Especially as we could have gotten a body through an opening that size."
 
There came a yell of triumph from Nikka, and Watkins, whose eyes had been straining at the opening, shouted:
 
"There is something there, your ludship!"
 
Nikka was digging furiously with the chisel at what looked to be a dark stone in the very center of the empty area.
 
"It's an inner wood panel," he grunted over his shoulder. "I can feel something behind it."
 
There was a splintering noise, and the "stone" fell apart. Behind it was a shallow recess, perhaps nine inches square, completely filled by a rusty iron box. Nikka levered the box out, and handed it to Hugh.
 
"Your ancestress was a clever old person," he commented, dropping beside us on the couch. "Fancy her figuring that the inner panel would prevent the recess from sounding hollow when it was rapped."
 
The box was about three inches deep. It was unlocked, and Hugh lifted the cover without difficulty. Inside were two papers, very brittle and yellow from the heat of the chimney. The first was a torn fragment from a household account book:
 
                                                            "Septr. ye 2nde, 1592.
"Paid Conrad of Nurmburgge ye Germanne masonne:
item, for sealinge ye Olde Cryptte belowe ye Priors
House: item, for ye engine for ye Priors Vent:
item, for ye pannellinge in ye Gunneroom £17 s9 d4
item, two boxes of Flanders iron s7
                                                                                          —————
"Accompte £17 s16 d4"
 
 
And below this was written:
 
 
 
"And I sent Hyme forth of ye Vilage thatte Hee might not have Chaunce to talk howbeeit Hee ys clousemouthed and Hath littel Englysh."
 
 
 
It was impossible not to laugh at the invincible determination of Lady Jane.
 
"What did she do with the second box?" I suggested.
 
"Probably used it in another mystery," chuckled Nikka. "What's the other paper, Hugh?"
 
"It's the real thing! Great Jupiter, see what Toutou missed!"
 
And he spread the second paper on his knee. It was short and to the point:
 
 
 
"To Hymne thatte hath Witte to rede Mye riddel. Presse atte ye One time ye Sfinxes headde and ye Monkes bellie. So wil ye Flaggin drop in ye Dexter side of ye Harth. Thatte whych you Seke you shal Discovour in yts proper Place.
 
"JANE CHESBY."
 
 
 
I flashed the electric torch on the mantle-piece. "Ye Sfinxes headde" was in the very center of the row of Turks' heads, and veiled women that was sculptured along the edge of the stone mantle-shelf. "Ye Monkes bellie" was the bit of carving that protruded from the center of the bibulous group that had upheld the panel bearing Lady Jane's verse.
 
"I've pressed both of those more than once," I protested.
 
"But not both at once," answered Nikka.
 
He bounded up, and drove his two hands, palm out, against the projections. There was a muffled thud in the fireplace. I sank on my knees, and trained the electric torch inside. On the "dexter," or right-hand side, in the rear, yawned a hole some two feet square.
 
I crawled through the ashes, and thrust the torch over the rim. There was a sharp drop of three or four feet, and then the beginning of a flight of stairs, heavily carpeted with dust. A damp, earthy odor smote my nostrils. The others crawled in beside me. Even Watkins pulled his nightshirt around him and stuck his head in as far as he could get.
 
"Ever seen that before, Watty?" asked Hugh, backing out.
 
"Never, your ludship."
 
The valet's face was a study.
 
"Is late ludship, Mister Hugh, was frequently in the 'abit of being alone, as I daresay you know. But 'ow in the world could 'e have found it, your ludship, if he didn't find out first about that?"
 
Watkins nodded toward the gaping hole in the over-mantle.
 
"I'm damned if I know," admitted Hugh. "Maybe we'll find out. By the way, how do you suppose you close the Vent?"
 
Nikka fingered the two projections, and the moment he applied pressure the flagstone slapped up into place.
 
"There's some counterweight arrangement," he said. "The fellow who designed this was a master-mechanic."
 
"Evidently," agreed Hugh. "Well, you chaps, we are another mile-stone farther on the road, but the first thing we have to do is to get the corpus delicti safely underground."
 
"Right," assented Nikka, "But we need clothes and food. You can't tell what we may run into."
 
For the first time I looked at myself, and burst out laughing at the spectacle I presented. My pajamas were torn to shreds, and I was smutted from head to foot with soot and ashes. Hugh and Nikka were little better. Watkins was as immaculate as a man in his night-shirt may be.
 
"Very well," said Hugh. "Then Jack had best go upstairs and wash, while Watkins gets dressed and fetches our clothes. In the meantime, Nikka and I can be disposing of our friend here."
 
We adopted this plan, and Watkins also volunteered to tell cook to start breakfast. The curtains had been close drawn over all the Gunroom windows, and I was amazed to perceive on leaving it that the sun was rising.
 
When I came downstairs twenty minutes later, Hawkins the butler, carrying a large tray, was knocking on the Gunroom door.
 
"I'll take it," I told him. "You go back to the kitchen like a good fellow, and keep the maids quiet."
 
I knocked for several minutes without result, and finally set the tray down, and banged the door with both fists.
 
"All right! All right!" called a strangely blanketed voice. "Who is it?"
 
"Jack!"
 
Feet scuffled inside, and the door was jerked open by Hugh, rather dusty and cobwebby.
 
"We were out under the Park," he explained. "We took that Gypsy down safely, and I came back ahead of the others on the chance you might be trying to get in. There's a regular passage, Jack. It seems to go on and on. We didn't have time to follow it very far."
 
He set the table, which I had overturned, on its legs, and I brought in the tray. Then Nikka and Watkins emerged from the fireplace, blinking owlishly, and we three drew chairs up to the table, and Watkins served breakfast as deftly as though we had not departed a hair's-breadth from the ordinary routine of life.
 
"Have you had breakfast yet, Watty?" asked Hugh.
 
"No, your ludship."
 
"Sit down, then, and eat."
 
Watkins looked like a man instructed to undress in Piccadilly.
 
"Beg pardon, your ludship—"
 
"Sit down, man."
 
"But, your ludship—"
 
Hugh pointed to a chair.
 
"Damn it, Watty," he said severely, "bring that chair up, pour yourself some coffee and eat."
 
Watkins complied with an air of outraged decorum.
 
There was a knock on the door.
 
"Who's that?" said Hugh.
 
"It should be 'Awkins with the quick-lime, your ludship," answered Watkins, hastily pushing back his chair. "'E had to 'ave it brought from the stables."
 
"Take it from him, Watty—and then ............