“I am going to see Mrs. Wilson, Ruth,” Bab declared.  “You had better stay here and do your best with Harriet.  The papers are not to be delivered until four this afternoon, when, I believe, Harriet is to meet Peter Dillon.  Of course it was he who telephoned Harriet, only he was clever enough to disguise his voice.  So we have until afternoon to work.  Don’t worry yourself sick.  We simply must save Harriet in some way.  I don’t pretend that I see the way clearly yet, but I have faith that it will come.  I cannot do any harm by going to Mrs. Wilson, and I may do some good.”

“I don’t like you to go there alone, Bab,” Ruth faltered.  “But I don’t dare to leave Harriet by herself.  She might find a way to give up the papers while we were out, and then all would be lost!”

When Bab rang the bell at the door of Mrs. Wilson’s home she did not know that her approach had been watched.  She meant to be very careful during her interview, for she realized that she and Ruth were endeavoring to foil two brilliant and unscrupulous enemies.

Mrs. Wilson and Peter were in the library, and through the window Mrs. Wilson had watched Bab approaching the house.

“Here comes that tiresome Thurston girl, whom you were going to use as your tool, Peter,” teased Mrs. Wilson.  “She wasn’t so easy to manage as you thought, was she?  Never mind; she will still be used as our scapegoat.  But I shall not see her this morning.  What’s the use?”

“Let her come in, by all means, Mrs. Wilson,” Peter Dillon urged.  “I shall hide so that she will not see me.  What would fall in with our plans better than to have this girl come here to-day!  Who knows how this visit may be made to count against her?  Of course, if suspicion never points to us we had best never mention the name of Barbara Thurston.  But—­if Mr. Hamlin ever questions you, why not say Miss Thurston came here to-day and betrayed the fact to you that she had stolen Mr. Hamlin’s papers?  We have circumstantial evidence enough against her.”

Bab found Mrs. Wilson very much surprised to see her, and looking very languid and bored.

Straightforward Barbara rushed headlong into her request.

“Really, Miss Thurston, don’t you think you are rather impertinent?” drawled her hostess, when Bab finished.  “I don’t see what business it is of yours whether or not I wish to play a joke on my friend, Mr. Hamlin.  Don’t try to get out of mischief by reporting to Mr. Hamlin the story of my poor little joke.  You can hardly save yourself by any such method.  No one will believe you.  And I have an idea that you came to my house to-day for a very different purpose than to persuade me to give up my joke.  What was it?”

Bab was mystified.  She had no idea how Mrs. Wilson and Peter Dillon had planned to use her visit as evidence against her, so it was impossible for her to understand Mrs. Wilson’s insinuation.

Barbara did not stay long.  She saw Mrs. Wilson had no intention of being persuaded from her design.  Even though the woman was beginning to see that Bab and Ruth were a little suspicious of her, she had no idea of being frightened from her deep-laid scheme by two insignificant schoolgirls.