Mr. Bangs made three calls on that memorable Monday. The first was to Billie, as you already surmise. If he recognized the strong undercurrent which connected the strange adventures of the Motor Maids during the past two months, he said nothing, but listened gravely to the young girl’s account of the happenings in Boulder Lane, the box of jewels, the cases of rifles at Seven League Island, and so on through the events which have been told in this history.

When Billie had finished, she paused and waited for the detective to speak, but he sat silently twirling his thumbs and looking down at the floor with half-closed eyes.

Billie was slightly irritated.

“I have sent for you, Mr. Bangs,” she continued with some dignity, “because, while I am certain of two things, I’m not at all sure of the third. The first is that Fannie Alta has some very good reason for trying to prove that Mary is a thief. The second is that this smuggler who has been trying to steal the jewels has something to do with it.”

“And what is the third, Miss Campbell?” asked the detective, smiling, without looking up.

“That is what I want you to tell me,” exclaimed Billie restlessly. “There is a third. It is the missing link. And it is what I wanted you to find out for me. I have thought and thought and puzzled and puzzled, but I can’t make it out. I believe with all my soul that there is some wicked force back of the whole thing.”

Mr. Bangs raised his eyes at last and looked at the young girl with evident admiration.

“You are taking the first step toward making a good detective, Miss Campbell,” he said. “You have expressed it in three words. It is the missing link we need to get at in this business and it is what I must find.”

Billie flushed with pleasure at this professional praise. She had never had occasion to play the part of detective before. But devotion and loyalty to her friend had sharpened her wits.

“Now, why?” asked the detective. “Isn’t Miss Alta the missing link?”

“That is the strangest part of the whole business. She is a piece of the link, I think, but then she has nothing against Mary and me. There would be no object to what she has done unless she had.”

“You did not know that she accused you of being the confederate of your friend or that she knew that you had the box of jewels hidden in the safe?”

“What?” cried Billie, with amazement. “But how did she know——” she began.

“Yes, how?”

Billie sat looking down at her hands. She was not thinking of those slender, strong fingers, which appeared to clasp each other with a friendly grip. Her thoughts were busy going back over the past few weeks.

“I think I’ve found the missing link,” she said at last, with a serious look in her eyes, as she turned toward the detective. “Belle Rogers is the missing link. I can’t understand why I haven’t thought of it before, but it seemed so incredible.”

“Miss Campbell,” put in Mr. Bangs severely, “I am afraid you are not such a good detective, after all. You have left out one of the most important things. You did not tell me that some one besides your three friends knew about the jewels.”

Billie had omitted the story of the confusion of the two suit cases at Shell Island. She had really quite forgotten it and Mr. Bangs chuckled with amusement when he heard how Belle had opened and examined all the contents of another girl’s suit case out of pure curiosity.

“Then she must have read the name on the card, too,” he said presently.

“I suppose so.”

“Now, tell me, Miss Campbell, what is the grudge which this young lady perhaps has against you and your friends?”

“Oh, it’s only a silly schoolgirl affair,” replied Billie. “I am ashamed to tell you, because it seems so utterly trivial in comparison to other things. She was angry because I wouldn’t join her club and because we saw her the night of the fire with her hair up in rubber curlers.”

The detective laughed outright.

“That’s a woman’s reason for taking revenge,” he said.

“And she was angry again because I took her into the wrong room, when the hotel was burning and we had to escape over the roof.”

“Humph!” exclaimed the detective. “Insult piled onto injury, eh? So this Miss Rogers is a very vindictive character?”

Billie hesitated. It went against her straight-forward, honest nature to malign even Belle Rogers.

“She has been spoiled all her life,” she said, “and you know how spoiled children must have their own way. That is all. She was angry because she planned to make me a member of her club and queen it over me as she does over the others, and I disappointed her. Her mother and friends have taken good care always that she should never be disappointed and she just didn’t know what the feeling was, I suppose.”

“She must be quite a remarkably spoiled young woman to go to such lengths for such a trivial offence. But we sometimes get in deeper than we intend, you know.”

The detective rose to go.

“Good day, Miss Campbell,” he said, giving her hand quite a warm grip, considering what a quiet, cold individual he had seemed at first. “You will hear from me again, soon. I had not intended to work when I came down here. You know I am a West Haven boy. My father was old Bill Bangs, the jailer. You probably have heard of him. He was a famous character in his day. I came home to rest and see my people, but when a detective scents a good case he is not apt to let it slip by, even on a holiday.”

“And you think this is a good case?”

“It’s a corking one,” he replied, as he closed the door after him.

Billie and Mary did not go to school that famous Monday. Billie had no mind to face the curious looks she felt certain would be turned upon her by the other girls, because news travels quickly in any school. Mary was lying on her mother’s bed with a throbbing sick headache. All day Mrs. Price sat beside her daughter and held her hand. At intervals she bathed her temples with eau de cologne and whispered:

“My dearest, it will come out all right. Mother loves you and believes in you and so does Billie. Don’t sob like that for my sake, my little girl.”

Belle Rogers also stayed at home that Monday. Mr. Bangs discovered this fact on his second visit of the day when he was closeted for an hour or more with Miss Gray and Mrs. St. Clair in the principal’s private office.

After a tiresome interview with these two well meaning but mistaken ladies, in which he said little and they said much, he left the High School with a sigh of relief.

Presently he found himself in the fashionable district of West Haven. It was the second time he had climbed the street that day, but he was a calm little person, not easily heated by emotion or exercise, and when he rang the bell at the Rogers home, there was just the suspicion of a smile on his face. He sent up his card for Miss Rogers and word was brought back that Miss Rogers was ill and not to be seen. Then, with a pencil, he wrote across the face of the card, “Lafitte—Paris.”

In three minutes the swish of skirts down the steps announced that some one was coming.

“I hope it’s not the mother,” he said to himself.

But it was Belle, very pale, with violet circles around her eyes and a nervous quivering about the lips.

When Mr. Bangs left the Rogers house after spending three-quarters of an hour with Belle, he remarked as he strolled down the gravel driveway to the street:

“It will have to be an out and out confession from one or the other. If this one doesn’t give it, the Alta girl must. I shall pay my respects to Mme. Alta this evening.”

He had hardly passed through the great iron gateway leading into the street, when Belle, wearing a heavy veil and a long ulster, hurried after him. She carried a music roll under her arm, although she was not taking lessons, since she had been injured in the fire, but it was understood by the servant who opened the door for her that she was going to see Mme. Alta.