"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 con？dence.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 Se？or Cristoval's of？ce，where he kept his books and his money—boxes."She rose，as she spoke，and looked uncertainly up anddown the wall.Then，with a nod of satisfaction，she quickly walked to the east corner and counted four blocks of adobe，starting from the ？oor.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 tothe secret rooms，but the key that unlocks it is somewhere in the ？oor.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 becausethe opening was so small.Inez followed her，nervously seizing the other girl's hand for support.The light seemed to comefrom some place far above and as their eyes grew accustomed to it they could discerna 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 leftthe 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 waswhen Se？or 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 lustyb cry.
"See to the baby，"said Mildred quickly，and the Mexican girl reluctantly turned away to obey.
Mildred remained in the recess，thoughtfully eyeing thevarious antique objects which had been allowed to remain there，some of which were of real value.She re？ected 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 advantageof her present opportunity.For here was the consummationa 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，holdinga 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 someone 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 thesound，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 ？rmly 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.