The four girls turned simultaneously.

The heavy door through which they had entered the cabin, and which was the only entrance, had been shut fast.  At the same instant there was the sound of a heavy, sliding bolt, then the rush of flying feet.

For the moment no one of the girls realized the seriousness of what had happened.

“Some one must have locked us in for a joke,” declared Phil stoutly.

Madge ran to the door and shook it with all her strength.  It was built of heavy logs, and, though the girls could see the daylight through the cracks between the timbers, the door showed no sign of opening.

“Don’t work so hard, Madge,” remonstrated Phil.  “Whoever shut us in will come back in a moment to unfasten the bolt.”

The girls waited a long time.  No one returned.

“Perhaps the person who closed the door did not know there was any one in the cabin,” suggested Eleanor faintly.

“But we were all talking, Nellie.  No one but a deaf person could have failed to hear us,” Lillian insisted.

Eleanor realized the truth of the words.

“Don’t be frightened, Nellie,” begged Madge remorsefully.  “Let’s all push against the door at the same time.  I am sure we shall be able to break the bolt.  One, two, three!  Now—­all together!”

The four girls shoved with all their might, until their arms ached and their faces perspired from the exertion.  Still the old door resisted them.  Perhaps Eleanor was right and the log house had been built as a prison.

“I think we had better call for help,” was Phil’s practical suggestion.  “If we all scream together, we ought to make considerable noise.  I am afraid Miss Jones may become worried about us before any one comes to let us out.”

The girls called and called, until their voices were hoarse, but no one answered them.  Each girl remembered that she had not met a single person in her journey through the woods.

Then the prisoners made a trip around the big room, poking and peering about to see if there were any other possible method of escape.

“If I could only get up to one of those windows, I could easily break the bars and try to jump out of it,” speculated Madge aloud.  “But, alas, I am not a monkey!  I can’t climb straight up the side of a wall.”

“You shall not try it, either,” retorted Eleanor determinedly.  “You would break your neck if you tried to jump from one of those high windows.  Thank goodness, you can’t climb up to them!”

“You were the wise one, Nell, and we wouldn’t listen to you.”  Madge eyed Eleanor mournfully.  She had an overwhelming desire to burst into tears.

“Don’t take it so to heart, Madge,” comforted her cousin.  “Some one is sure to come this way finally, if we only call long enough.”

But the afternoon shadows lengthened and no one came.  Gradually the twilight fell, enveloping the big, bare room in hazy darkness.  The prisoners huddled together with white and weary faces.  They thought of their cosy houseboat with the little lamps lit in the dining room, and the big lantern hanging in the bow, and of Miss Jones, who by this time was no doubt anxiously waiting and watching for their return.