mrs. vernon's house was built in the shape of a letter l, the lady's wing containing the library and business office downstairs and private apartments on the second floor.

when robert let himself into the house he entered the library to find out if the lady had yet returned.

nothing was disturbed, and he was about to walk into the business office, when on looking out on the street he saw frederic vernon standing behind a nearby tree, watching the mansion closely.

"hullo," cried robert to himself. "what is he up to now?"

at first he thought to go out and hail vernon, but quickly changed his mind.

"i'll get nothing out of him by questioning him," he reasoned. "it will pay far better to watch him and see what he does and where he goes."

a few minutes after our hero had discovered vernon, he saw the spendthrift hurry swiftly for the wing of the house and try the window to the business office.

the sash was locked, but by inserting a knife blade between the upper and lower sashes he was enabled to push the catch back.

this done the lower sash was raised, and frederic vernon crawled into the business office as silently as a cat.

"he is up to no good," said our hero to himself. "i believe he is here to steal something."

there was a large turkish chair handy, and robert crouched behind this, that frederic vernon might not see him should he take a peep into the library.

"don't seem to be anybody around," he heard vernon mutter, as he looked into the library. "frost must be off trying to hunt the old woman up."

vernon tiptoed his way to mrs. vernon's desk, and, unlocking it, slid back the roller top.

the movement surprised robert, for he had thought that only mrs. vernon and himself had keys to the desk.

"perhaps he is using mrs. vernon's key," he thought.

with great rapidity frederic vernon went through several drawers full of papers.

"pshaw! the papers must be in the safe," he murmured, and leaving the desk he approached the safe, which stood in a corner. getting down on his knees he began to work at the combination.

"thirty-five twice, twelve three times," he murmured, repeating what had once been the combination of the lock.

but mrs. vernon had had robert to change the combination just before starting for england, and consequently frederic vernon failed to get the door open.

he fussed with the combination for a quarter of an hour, getting more angry over his failure every minute.

"confound the luck, they must have changed it," he muttered. "i wish i dared to tackle frost about it. but i am not quite ready for that. perhaps i can make her give me the combination."

robert did not hear the last words, yet he felt pretty certain that frederic vernon was responsible for his aunt's disappearance, and knew where she was.

he was half of a mind to call in a policeman, yet he was afraid that vernon might in some manner give the officer of the law the slip.

"and if he is locked up now he may deny knowing anything about his aunt," was the boy's conclusion.

at last vernon left the safe and went to the desk once more. here he selected several papers and rammed them in his pocket. then, without warning, he slipped out of the window again, closed the sash, and started down the street at a brisk pace.

"i'll follow him," said robert to himself. "and i won't leave him out of sight until i've found out what has become of mrs. vernon."

running into the upper hallway robert saw on a rack an old overcoat he had once worn and a slouch hat which had belonged to another inmate of the mansion.

he donned these, pulling the hat far down over his forehead, and the coat up around his neck. then he put on a pair of blue glasses which mrs. vernon had used on the sea voyage to protect her eyes from the glare of the sun on the water.

thus partially disguised, he made after frederic vernon, who had now reached the block below the house.

here vernon took a passing car and took a seat inside.

running rapidly, robert managed to catch the car, and took a position on the rear platform, with his back to the interior, that the young spendthrift might not see his face.

the car was one running well on toward the southern outskirts of chicago, and vernon remained in it until the very end of the line was gained.

then he walked on once more, with robert still dogging his footsteps, but so carefully that the young man never suspected he was being followed. once he looked back, but our hero promptly stepped out of sight behind a nearby billboard.

in this district the houses were much scattered, and most of them were surrounded by large gardens.

frederic vernon passed into a side street which was little better than a road, and soon reached a large square building of stone, set in a perfect wilderness of trees and bushes. a high iron fence surrounded the ill-kept garden, and the single iron gate was locked.

ringing a bell at the gate, frederic vernon thus summoned a porter, who came, and after asking him a few questions, let him in.

approaching the gate, robert saw a sign over it, in gilt letters, which read in this fashion:

dr. nicholas rushwood,

private sanitarium for the weak-minded.

peering through the ironwork, our hero saw frederic vernon follow the porter up the steps of the stone building and disappear inside.

"this must be the place to which mrs. vernon has been taken," thought robert.

he waited at the gate for awhile to see if frederic vernon would come out, but the young spendthrift failed to put in an appearance.

the sanitarium was located on a corner, and ran from one street to the next, so that our hero could walk around three sides of the place. on the other side was a high stone wall, which separated the asylum grounds from those of a well-kept garden.

all of the windows on the second and third stories of the stone building were very closely barred.

"they must keep the patients up there," concluded robert.

he gazed sharply at each window, but though he saw several men and women, he did not catch sight of mrs. vernon.

presently a butcher boy came along the back street, a large basket on his arm.

"can you tell me what place this is?" questioned robert.

"that's dr. rushwood's asylum for crazy folks," answered the butcher boy.

"has he many patients?"

"ten or a dozen, i believe."

"were you ever inside of the place?"

"i used to deliver meat there. but our firm don't serve him any more."

"and what kind of a place is it?"

"it's a gloomy hole, and the doctor is a terror."

"a terror? what do you mean by that?"

"he's awfully strict and awfully mean. some folks say he don't give the crazy folks half enough to eat. he was always kicking about his meat bill. that's the reason our firm stopped serving him."

"did you see them taking anybody new into there lately?"

"no, but i heard jack mason telling that he saw them taking a woman in there last night."

"a young woman or an elderly lady?"

"jack said it was an oldish-looking woman, and said she was very handsomely dressed."

"what time was this?"

"about six o'clock last night. they brought her in a coach, and two men were with her. but what do you ask all these questions for?"

"i have my reasons. a lady has disappeared and i am looking for her."

"christopher! did they abduct her?"

"i don't know. i am much obliged to you," returned robert, and to avoid being questioned further he sauntered off. he did not go far, however, and as soon as the butcher boy was gone, he returned to the vicinity of the sanitarium.

it was now growing dusk, and watching his chance he climbed to the top of the stone wall which divided the asylum grounds from that of the garden next door. the top of the wall was rough, but with care he managed to walk from one end to the other.

while he was on the wall he heard the gate bell ring, and crouched down to get out of sight. the porter admitted two men, but who they were robert could not see.

from the wall robert could easily look into the lower windows of the building. one room into which he gazed was fitted up as a library, and as he gazed into it the door opened and four men entered.

the four men were frederic vernon, dr. remington, and two others, the keeper of the asylum and a second physician.