Through consideration for the nerves and perhaps the credulity of the reader, it may be advisable at this juncture to go a little back in our story and relate the circumstances which led to the present perplexing crisis. A great detective once said that “every mystery has a simple solution”—meaning, of course, that the solution is simple when once discovered. Therefore, the puzzling mystery of the disappearance of baby Jane and her two nurses, followed later by the vanishment of Mr. Bulwer Runyon, was due to the one-time idiosyncracy of a certain SeÑor Cristoval, happily deceased, rather than to any supernatural agency.

Until now we have only known Mildred Travers, as she called herself, in a casual way. We know that she was considered a competent nurse and had proved her capability in the care of baby Jane. Also we know that she was silent and reserved and that her eyes bore an habitual expression that was hard and repellent. Without being able to find any especial fault with the girl, no one was attracted toward her—always excepting the baby, who could not be expected to show discrimination at her tender age.

A little of Mildred’s former history had escaped her, but not enough to judge her by. She had once lived in Southern California, near this very place. She had visited this house frequently with her father, when a small child, and old SeÑor Cristoval had confided to her some of the secrets of the mansion. That was all. What had become of friends and family, how she went to New York and studied nursing, or what might account for that hard look in her eyes, no one now acquainted with her knew.

The Mexican girl, Inez, was nearly as peculiar and unaccountable as Mildred. There was no mystery about her, however, except that she was so capable and intelligent, considering her antecedents. Inez’ people lived in a small town in another part of the county and the girl was one of a numerous brood of children whose parents were indolent, dissipated and steeped in ignorance. When fourteen years old she had left home to work for some of the neighboring ranchers, never staying in one place long but generally liked by her employers. The woman who had recommended Inez to Mrs. Weldon said she was bright and willing and more intelligent than most Mexicans of her class, but that she possessed a violent temper.

Louise had seen little evidence of that temper, however, for Inez from the first loved her new mistress and idolized the baby. It was only after Mildred came to supplant her, as she thought, that the girl developed an unreasoning, passionate hatred for the other nurse and was jealous of every attention Mildred lavished upon the little one.

The baby was impartial. She laughed and held out her chubby fists to either nurse, perhaps realizing that both were kind to her. It was this that made Inez so furious and caused Mildred to disdain the Mexican girl. The two were at sword’s points from the first, although after a little Mildred made an attempt to conciliate Inez, knowing that the untutored Mexican was by nature irresponsible and jealous, but withal loving and generous.

Inez did not respond to these advances, but as the days passed she became less sullen when in the presence of Mildred, and at times, when busied over her duties, so far forgot her animosity as to converse with her in her old careless, unaffected way. Only Mildred was able to note this slight change, and it encouraged her to believe she might win Inez’ confidence in the end. Inez herself did not realize that she had changed toward the “witch-woman,” and when brooding over her fancied wrongs hated Mildred as cordially as ever.

On the day when the Weldons and their guests rode into town, the two nurses had indulged in a longer and more friendly conversation than usual. It began by Mildred’s chiding the Mexican for taking baby to the quarters unknown to her, as she had been obliged to follow to see what had become of the child. Inez retorted by accusing Mildred of spying upon her. Their return to the house was anything but friendly, and Inez flatly refused to obey such instructions as Mildred gave her for the care of baby. She even walked out of the court in a temper and was gone for an hour. Then she stole in, a little ashamed of her revolt, but still defiant and rebellious.

They were in the nursery and Mildred pretended not to notice her assistant’s mood.

“I have prepared two bottles of baby’s food,” said she. “Please place one in the hollow of the wall, in your room, to keep cool until we need it.”

“I won’t!” said Inez.

“Why not?” asked Mildred quietly.

“Because you are witch-woman,” cried the Mexican; “because you use bad magic to make hollow in wall; because you try to make baby witch-woman, like yourself, by keeping her milk in the witch-place; because—because—I hate you!” she concluded with a passionate stamp of her foot.

Mildred looked upon the girl pityingly as she crossed herself again and again as if in defiance of the supposed witchcraft. The poor girl sought by this method to ward off any evil charm Mildred might attempt in retaliation, and the action nettled the trained nurse because the unjust accusation was so sincerely made.

She slowly rose and taking the bottle of milk carried it herself to the hollow in the wall and placed it upon a shelf. Then, returning, she stood before the petulant, crouching Mexican and said gently:

“Were I truly a witch, Inez, I would not be working as a nurse—just as you are. Nor do I know any magic, more than you yourself know.”

“Then how you know about that hole in the wall?” demanded Inez.

“I wish you would let me explain that. Indeed, I think a good talk together will do us both good. Take this chair beside me, and try to believe in my good will. I do not hate you, Inez. I wish you did not hate me.”

Inez slowly rose from the floor and seated herself in the chair, turning it so that she could eye Mildred’s face as she spoke.

“When I was a girl,” continued Mildred, “I often came to this house to visit. Sometimes I stayed here for several days, while my father talked with his old friend, old SeÑor Cristoval.”

“That is a lie,” asserted Inez. “I have ask Miguel, who is here forty years, an’ was house servant for SeÑor Cristoval. Miguel say there is no SeÑor Travers who is friend of SeÑor Cristoval. No SeÑor Travers did ever come to this house for visit. What you say to that, Witch-Woman?”

Mildred flushed and seemed embarrassed. Then she answered calmly:

“I think Miguel speaks truly, for my father did not bear the name of Travers. He was called by another name.”

“Then why do you call yourself Travers?” retorted the other.

Mildred hesitated.

“I did not like my old name,” she said, “and so I changed it. But this is a secret I have told you, Inez, and you must not tell anyone of it.”

Inez nodded, looking at the other curiously. This confession had aroused her sympathy, for the first time, for her fellow nurse. The fact that there was a secret between them dissolved to an extent her antipathy for Mildred, and it might be a bond to eventually draw them nearer together. With more tolerance than she had yet shown she asked:

“Did SeÑor Cristoval show you the secrets of this house?”

“Yes. I was a little girl and he was good to me. I am not a witch-woman, Inez. Oh, if I were, I would witch a little happiness into my life!” she added miserably.

This burst of rebellious longing interested Inez even more than the secret. She could understand such a protest against fate.

“At first,” continued Mildred, reverting to her former cold speech, while the hard look, which for an instant had given way to a flash of sentiment, again crept into her eyes, “I thought I had forgotten the queer recesses and secret rooms built by the elder Cristoval; but now I am beginning to remember them. In the days when this wing was built, the country was wild and lawless. Robbers often visited a house in broad daylight and took away all that was of value; so the first Cristoval—the father of the one I knew—made the secret place to hide his treasure in, and even to hide himself and his family if the thieves threatened them.”

“Is the treasure there now?” asked Inez eagerly.

Mildred frowned, as if the question displeased her.

“Of course not. That was long ago. When I was a girl they no longer needed the rooms in the wall as a hiding-place from thieves; but they kept them secret, just the same. I think I am the only person SeÑor Cristoval ever told. He did it to please me, I suppose, because I was a child.”

Inez was much impressed. She began to regard Mildred more amicably. If she were not a witch-woman, she reflected, there was no reason to fear her. The Mexican girl thought deeply on what she had heard, during the next half hour. She watched Mildred put the baby to sleep and then take up a book to read as she sat beside the crib. Inez went out into the deserted court and squatting beside the fountain pondered upon the fascinating mysteries of the old house.

She crept back, presently, and reentered the nursery where Mildred was sitting.

“Tell me,” she began, in a friendly and familiar way that was new in her relations with the other girl, “are there indeed rooms hidden in these walls—big enough for people to hide in?”

Mildred smiled and laid down her book. Inez in this mood was worth cultivating, if she hoped to win her confidence. It would be far easier to get on in her new situation if Inez would learn to like her.

Another thing influenced her: a reflection that had not been absent from her mind since the Weldons departed for the day and had left her practically in charge of the house. She had come to this house for a purpose. Could that purpose be best accomplished to-day, or at some later period?

“I believe,” she answered musingly, “that this wall back of us is hollow and contains several rooms, which may be entered at various secret places—if one knows where the places are.”

“They cannot be very big rooms,” said Inez in a hushed, awed voice, as she glanced at the wall.

“No; they must be narrow. But they are quite long and high—some of them—and there are stairs leading from one floor to another, just like the big stairs in the hall.”

Inez stared at her.

“How you know that?” she inquired.

“Why, I’ve seen the rooms,” was the reply. “Let me think a moment.”

During the pause she scrutinized the Mexican girl closely, wondering if it would be advisable to take her into her confidence. Then she continued, speaking slowly:

“I’m almost sure it was in this very room that one of the secret entrances was built. It was not a nursery when I was here before, you know; it was SeÑor Cristoval’s office, where he kept his books and his money-boxes.”

She rose, as she spoke, and looked uncertainly up and down the wall. Then, with a nod of satisfaction, she quickly walked to the east corner and counted four blocks of adobe, starting from the floor. The fourth line of blocks she followed to the third one, and placed her hand upon it.

“I think I am right, so far,” she said. “This is the door to the secret rooms, but the key that unlocks it is somewhere in the floor. Turn back the rug, please, Inez.”

The girl obeyed, her brown fingers trembling with excitement. The floor was of adobe blocks similar to those which formed the wall, but smaller in size. Mildred regarded them reflectively and then placed her foot on the edge of the second block directly in a line with the place where her hand rested. The pressure of her foot made the block tip slightly, and observing this she pressed hard with her hand against the inner edge of the upper block.

The result seemed magical. Three seemingly solid blocks of the wall swung slowly outward, disclosing a dimly lighted recess beyond.

Mildred stepped in, stooping her head slightly because the opening was so small. Inez followed her, nervously seizing the other girl’s hand for support. The light seemed to come from some place far above and as their eyes grew accustomed to it they could discern a passage about three feet in width and fourteen feet long, which occupied the center of the wall. At the right, a flight of steps led upward, and to their left the place was occupied by some chairs and stools. Against the walls were several narrow shelves, easily reached by one standing upright.

“Why, they have left the place furnished, just as it was when SeÑor Cristoval first showed it to me,” said Mildred. “The mattings and upholstery must be ready to fall to pieces, by this time; but you see, Inez, I was right about the secret rooms.”

Just then little Jane wakened with a lusty cry.

“See to the baby,” said Mildred quickly, and the Mexican girl reluctantly turned away to obey.

Mildred remained in the recess, thoughtfully eyeing the various antique objects which had been allowed to remain there, some of which were of real value. She reflected that the last Cristoval had doubtless passed away without disclosing the secret of the wall to anyone, and his executors, in selling the mansion, had been quite unaware that anything was hidden in the adobe wall. Without doubt the property might now be justly claimed by the new owner, Arthur Weldon, and this thought made Mildred flush with eager resolve to take full advantage of her present opportunity. For here was the consummation of her hopes; here was the realization of the important plan which had brought her to Southern California and to this house.

Inez had caught the baby from its cradle and, holding a bottle of fresh milk-food to its lips to comfort it, again advanced through the opening. Mildred had stepped a few paces along the passage and Inez, the baby in her arms, started to join her.

At that moment she heard a sound in the court, as of some one approaching, and to avoid letting others know of this fascinating secret the girl thoughtlessly grasped the adobe door with her free hand and swung it shut behind her.

It closed with a sharp “click!” and Mildred, hearing the sound, turned with a low cry of fear.

“Great heavens, what have you done?” she exclaimed in tense tones and brushing the Mexican aside she threw her whole weight against the wall. It did not yield a hair’s breadth.

Inez, with terror in her eyes, stared at her companion.

“Is it lock?” she whispered.

Mildred pushed again, straining every muscle. Then she bent and examined the wall. It was easy to see, from this side, where the series of three blocks were firmly joined together. Also the butts of three huge iron hinges protruded slightly into the passage. There could be no mistake. The closing of the door had made them prisoners.