As a matter of fact, however, the detectives had little to do on Saturday and Sunday.  Only three of the girls made shopping trips on Saturday and all took an automobile ride Sunday afternoon.  This was the sum total of their activities away from the Stanlock home, with the exception of one instance, of which there was no hint until late in the afternoon.

About six o’clock Marion suddenly became mindful of the fact that she had not seen Helen since their return from the automobile drive three hours earlier, and she began a search for her.  She first went upstairs to her room to see if her friend were there.  Probably she was tired and had lain down to rest and fallen asleep.  But an inspection of the room failed to discover Helen.

Considerably puzzled, Marion now hunted up every other person in the house and inquired for the missing girl.  Not one of them remembered seeing her since the return from the drive.  The girl hostess was now thoroughly alarmed and her fears were speedily communicated to the others.  Everybody joined in the search and every nook and corner capable of concealing a human form was examined.

Helen Nash was not in the house and there seemed to be no reasonable explanation of her disappearance.

* * * * *

CHAPTER XIII.

“Find her, or I’ll find her myself.”

Mr. Stanlock came home from a meeting of mining stockholders about the time when consternation over the disappearance of Helen was at its height.  After the particulars of the affair, so far as they were known, had been explained to him, he asked: 

“Where are the detectives?”

The question fell with something of a shock on the ears of the assembled searchers who had just completed a second fruitless hunt through the house.  Why had they not thought of the trio of “mystery masters” before?

“We ought to have called them in at once,” Mrs. Stanlock said.  “I suppose they’ve gone by this time, but I’ll see.”

She pushed the buzzer button in the hall and soon the new chauffeur appeared at the side entrance.  Yes, the detectives had gone, but he knew where they could be found—­at the High Peak Athletic Club.

Mr. Stanlock at once called up the club and soon had one of the detectives on the wire.

“Can you men come over at once?” he inquired.  “One of the girls has disappeared and we are afraid that something serious has happened.”

“Yes, we’ll be there right away,” was the answer.

Twenty minutes later there was a ring at the door and the three detectives, a tall thin man, a short heavy man, and a squarely built angular man, were ushered in.

The short heavy man, named Meyers, was the most talkative of the three.  He put forth a string of questions as to when and where Helen was last seen and what she was doing.  Had anybody seen her go out of the house?  Nobody had.  Was there anything peculiar in her manner in the course of the day?  Nothing peculiar.  What kind of a girl was she?  What were her most noticeable characteristics?  Had she any pronounced likes and dislikes?  Was she in the habit of doing things just to be contrary?  Was she a girl of good judgment, or flighty and light-headed?