At Harriet’s request Bab and Ruth went silently out of her room, their faces white and frightened.

“Ruth, is there any place where we can be alone?” Barbara whispered faintly. “I must talk with you.”

Ruth nodded, and the two friends found their way into the library, turning the key in the lock. Then they stood facing each other, speechless, for a moment, from the very intensity of their feelings.

“Ruth, you must do something,” Bab entreated. “The papers that Mrs. Wilson and Mr. Dillon are making Harriet get for them they do not intend to use for a joke. Oh, Ruth, they are no doubt important state papers! Harriet may be betraying her country and ruining her father by placing these papers in their hands.”

“I think, too, that Mrs. Wilson and Peter Dillon are spies,” Ruth returned more quietly. “And, of course, we must do something to prevent their getting their hands on the papers.”

“But what can we do?” Barbara demanded sharply. “We cannot tell Mr. Hamlin of Harriet’s deed. It would be too cruel of us. Nor can we confront Mrs. Wilson and Peter Dillon with the accusation. They would only laugh at us, and declare that we were mad to have imagined any such thing. Then, again, we would be betraying Harriet’s confidence. We do not know just what state papers Harriet is to give to them, but they must be very, very valuable. I suppose those dreadful people will have the papers copied, sell our country’s secret, and return the papers to Harriet when all the mischief has been done. Ruth, I believe, now, that Mrs. Wilson and Peter Dillon both meant to make me steal Mr. Hamlin’s papers. Then they would have declared I had sold them to some one. And Mr. Hamlin would never have suspected his friends. Now, they think poor Harriet will be too much afraid to betray them.”

Bab’s voice trembled slightly. She realized how nearly she had been the dupe of these two clever schemers. She felt that she and Ruth must save Harriet at all events.

“Mrs. Wilson tried to steal Mr. Hamlin’s papers the night she masqueraded as a ghost,” Barbara continued. “I picked up the envelope she dropped on the floor in the hall.”

“I know it, Barbara,” Ruth answered in her self-controlled fashion, which always had a calming effect on the more impetuous Bab. “I also believe Mrs. Wilson meant to fix the guilt of the theft upon you. Uncle William called me into his study the other day and asked me if I considered you trustworthy. Of course I was awfully indignant and told him just what I thought of him for being so suspicious. But I believe Mrs. Wilson had tried to poison his mind against you. You must be on your guard now, Bab, dear. If Harriet gives up these papers of Uncle’s the plotters may still try to use you as their scapegoat. When Uncle finds his papers have disappeared Mrs. Wilson and Mr. Dillon will, of course, appear to know nothing of them; but they will somehow try to direct suspicion against you, trusting to Harriet’s cowardice. Don’t you worry though, Bab, dear. You shall not suffer for Harriet’s fault while I am here.”

“Oh, I am not worrying about myself, Ruth,” Bab answered. “It is Harriet’s part in the affair that troubles me. Do, please, go to Harriet and talk to her again. Surely you can make her see the risk she is running. Do you suppose it would do any good if I were to call on Mrs. Wilson? I could just pretend I still thought she meant to play the joke on Mr. Hamlin. You know she told me she intended to do so. I could beg her to give it up without mentioning Harriet’s name or letting Mrs. Wilson guess that Harriet had confided in us.”

Ruth shook her head. “It would not do any good for you to go to Mrs. Wilson, Bab. And, somehow, I am afraid for you. We do not know how much further they intend to involve you in their plot.”

“Oh, they won’t do me any harm, now,” Barbara rejoined. “Anyhow, I am willing to take the risk, if Harriet will not give in.”

“Just wait here, Bab, until I have been to see Harriet again,” Ruth entreated. “I will go down on my knees to her, if I can persuade her to give up this wicked deed. Oh, why is she so determined to be so reckless and so foolish?”

Fifteen minutes afterwards Ruth came back from her second interview with Harriet, looking utterly discouraged. “Harriet simply won’t give up,” Ruth reported to Bab. “She is absolutely determined to go her own way, and she is angry with me for interfering. Oh, Bab, what will happen? Uncle is so proud! If his daughter is known to have given Mrs. Wilson and Peter Dillon state papers, the report will be circulated that she stole them, and Uncle William will be disgraced. Then, what will become of Harriet? She does not intend to do wrong. But I simply can’t make her see this thing as we see it. So what can we do?” Unusually self-contained, Ruth broke down, now, weeping on Bab’s shoulder. The thought of the dreadful disgrace to her uncle and her cousin was more than she could face.

“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.

Barbara hurried to her car as fast as she could, anxious to get back to Ruth and to devise some other move to checkmate the traitors. She even hoped, against hope, that Harriet had been induced to change her mind and that all would yet be well. But as Bab jumped aboard her car she saw another girl, running down the street, waving something in the air and evidently trying to induce Bab’s street car to wait for her. Barbara begged the conductor to hold the car for a moment, before she recognized the figure, running toward them. But the next second she beheld the ever-present newspaper girl, Marjorie Moore, tablet and pencil in hand, completely out of breath and exhausted. Marjorie Moore could not speak for some time after she had secured a seat next Bab in the car.

“I have been watching Mrs. Wilson’s house since eight o’clock this morning,” she finally gasped. “What on earth made you go in there?”

“I can’t tell you,” Bab returned coldly. Not for anything in the world would she have Marjorie Moore suspect what she and Ruth feared.

Miss Moore gave a little, half amused, half sarcastic laugh. “You can’t tell? Oh, never mind, my dear. I know you are all right. You weren’t doing anything wrong. I expect you were trying to help set matters straight. You don’t need to tell me anything. I think I know all that is necessary. Good-bye now. I must get off this car at the corner. Let me tell you, however, not to worry, whatever happens. I am in possession of all the facts, so there will be no trouble in proving them. But if anything disagreeable happens to you,” Marjorie Moore gave Bab a reassuring smile, “telephone me, will you? My number is 1607, Union.”

Marjorie Moore rushed out of the street car as hurriedly as she had entered it, before Bab could take in what she had said.

Barbara puzzled all the rest of the way home. Could it be possible that Marjorie Moore had discovered Mrs. Wilson’s and Peter’s plot? Could she also have guessed Harriet’s part in it? Bab shuddered, for she remembered the newspaper girl’s words to her on the night of their first meeting: “If ever I have a chance to get even with Harriet Hamlin, won’t I take my revenge?” Did Marjorie Moore also suspect that an effort would be made to draw Barbara into this whirlpool of disgrace?

No one ate any luncheon at the home of the Assistant Secretary of State, except Mollie and Grace. Fortunately Mr. Hamlin did not return home. Ruth and Bab had decided not to tell the other two “Automobile Girls” of their terrible uneasiness unless they actually needed the help of the younger girls to save the situation. Ruth and Bab did not wish to prejudice Mollie and Grace against Harriet if it were possible to spare her. But Ruth had told Bab that, at four o’clock, Harriet was determined to deliver the papers to Peter Dillon.

At two o’clock, however, the two friends had found no way to influence Harriet to give up her mad project. Indeed, Harriet scarcely spoke to either of them, she was so bitterly angry at what she termed their interference.

At three o’clock, Ruth and Barbara grew desperate. For, at three, Harriet Hamlin closed the door of her bedroom and commenced to dress for her engagement.

“Try once again, Ruth,” Bab pleaded. “It is worse even than you know. I believe Marjorie Moore suspects what Harriet is about to do. Suppose she publishes the story in the morning papers. Tell Harriet I have a reason for thinking she knows about the affair.”

Bab waited apprehensively for Ruth’s return. It seemed to her that, for the first time in their adventures, the “Automobile Girls” had met with a situation that no amount of pluck or effort on their part could control. This was the most important experience of their whole lives, for their country was about to be betrayed! Once Barbara stamped her foot in her impatience. How dared Harriet Hamlin be so willful, so headstrong? Bab’s face was white with anxiety and suspense. Her lips twitched nervously. Then in a flash her whole expression changed. The color came back to her cheeks, the light to her eyes. At the eleventh hour the way had been made clear.

Ruth had no such look when she returned to Barbara. She flung herself despondently into a chair. “It’s no use,” she declared despairingly. “Harriet must go her own way. We can do nothing with her!”

“Yes, we can!” Bab whispered. She leaned over and murmured something in Ruth’s ear.

Ruth sprang to her feet. “Barbara Thurston, you are perfectly wonderful!” she cried. “Yes, I do know where it is. Go to my desk and take that blank paper. It is just the right size. Fold it up in three parts. There, it will do, now; give it to me. Now go and command Grace and Mollie, if they love us, to call Harriet out of her room for a minute. We can explain to them afterwards.”

Mollie and Grace feared Barbara had gone suddenly mad when she rushed in upon them with her demand. But Mollie did manage to persuade Harriet to go into the next room. As Harriet slipped out of her bedroom, her cousin, Ruth Stuart, stole into it, hiding something she held in her hand. She was alone in Harriet’s room for not more than two minutes.

At a quarter to four o’clock, Harriet Hamlin left her father’s house with a large envelope concealed inside her shopping bag. Opposition had merely strengthened Harriet’s original resolution. She was no longer frightened. Ruth and Bab were absurd to have been so tragic over a silly joke.

At a little after four o’clock, in a quiet, out-of-the-way street in Washington, Harriet turned over to Peter Dillon this envelope, which, as she supposed, contained the much-coveted papers which she had extracted from the private collection of the Assistant Secretary of State.

Whatever the papers were, Peter Dillon took them carelessly with his usual charming smile. But inwardly he was chanting a song of victory. He and Mrs. Wilson would be many-thousands of dollars richer by this time to-morrow. He glanced into the envelope with his near-sighted eyes. The papers were folded up inside and all was well! Peter did not dare, before Harriet, to be too interested in what the envelope contained.

It would not have made him happier to have looked closer; the song of victory would have died away on his lips. For, instead of certain secret documents sent to the office of the Secretary of State, from representatives of the United States Government in China, Harriet Hamlin had turned over to Peter Dillon an official envelope, which contained only folded sheets of blank paper!

It had been Barbara’s idea and Ruth had carried it out successfully. In the moment when Harriet left her room in answer to Mollie’s call, Ruth had exchanged the valuable state papers for the worthless ones. Once Harriet was safely out of the way, she and Bab carried the precious documents downstairs and shut them up in Mr. Hamlin’s desk. Both girls hoped that all trouble was now averted, and that Mr. Hamlin would never hear of Harriet’s folly!