It was not long before there came a recurrence of the strange humming noise which had so disturbed the girls. It was only a few nights later that Chet sat up in bed with the joyful feeling that here at last was a chance to investigate at least one of the ghosts that haunted the homestead at Cherry Corners.

“Ferd! Teddy! Wake up! What’s the matter? Are you dead?” he called to the boys.

The latter reluctantly opened their eyes and looked at him reproachfully.

“Can’t you let a fellow sleep?” Teddy asked. But Chet, with no ceremony whatever, hauled him bodily out of bed and set him on his feet.

“Don’t talk,” he ordered. “Run as fast as you can to the roof before we miss it.”

“What are you raving about?” asked Ferd, although both he and Teddy started obediently toward the attic stairs.

“If you wouldn’t talk so much, you could hear it,” Chet answered, pushing up a trap door that led to a small square platform on the roof. “It’s the motor sound the girls heard and that scared them so.”

“It is, for a fact!” cried Teddy in a joyful whisper. “And it’s coming right near, fellows, too.”

“It’s an aeroplane all right,” said Ferd, with conviction. “Nothing else ever made a noise like that.”

“Say, what are you doing up there?” a girl’s voice hailed them from the bottom of the steps, and Chet thought he recognized it as Billie’s. “Are you walking in your sleep or have you gone crazy? Come down here quick, we need you.”

“Keep still,” Chet yelled back. “We’re looking for your aeroplane ghost. Can’t you hear it?”

“Yes. But, oh, Chet,” Billie’s voice was tremulous, “the piano is playing itself again. Won’t you come down? We’re afraid to stay here all alone.”

“Great Scott! all the spirits are roaming at once,” cried Teddy, straining his eyes to see through the darkness as the humming of the motor came nearer.

“There, isn’t that it?” cried Ferd, pointing eagerly through the trees toward a little patch of sky, palely illumined with stars.

“I think I saw it,” said Chet, rubbing his eyes impatiently. “It’s so confoundedly dark-”

“Oh, won’t you please come down?” wailed Billie’s voice from the spooky depths of the attic. “I’ll die of fright if I have to stay here another minute.”

This appeal moved the boys, and they began reluctantly to descend the ladder, keeping their eyes all the time on the pale patch of sky.

“Where are the others?” asked Teddy, as he reached Billie’s side.

“They’re down looking for the ghost,” answered Billie, as she ran down the stairs in front of them. “They sent me to get you boys, and I found you gone. Mrs. Gilligan,” she added, with a hysterical giggle, “has the broom and Laura has the poker.”

“Maybe we’d better stop on the way and gather up a few bedposts,” suggested Ferd, as they took the last flight of stairs on a run and landed in the lower hall.

“Hello, did you find anything?” sang out Chet, as the girls, looking scared but valiant, came out to meet them. “Where’s Mrs. Gilligan?”

“Inside,” said Violet. “There isn’t a thing to be seen any more than there was the other night. I’m absolutely positive now that it must be a ghost.”

“Well, if it is, he’s got a sense of humor,” said Mrs. Gilligan, rising from her knees where she had been peering into the corner behind the piano. “I’ve heard of all sorts of spirits, but I never heard of one who insisted upon playing the piano in the dead of night.”

“He must have been a musician in his life time,” suggested Chet. “That’s the reason he comes and haunts the piano.”

“Well, I don’t see why he doesn’t choose a regular piano to haunt,” said Billie, feeling irritable because she was very sleepy and had been very much frightened. “It’s bad enough for a live person to play, let alone a ghost.”

“And where could it have gone?” wondered Laura, her eyes big and dark with excitement. “The minute we heard the noise-I guess we’re sort of listening for it even in our sleep-we jumped up and came down here while Billie went to call you boys. It was playing almost up to the minute we came into the room.”

“And maybe we weren’t afraid to go in!” said Violet, with a shudder. “I don’t know how we ever got the courage.”

“Well, you only came because Mrs. Gilligan and I went ahead with the broom and the poker,” sniffed Laura.

“Was it playing when you came down the stairs?” asked Chet, interested. “And did it stop as soon as you entered the room?”

“Yes,” it was Mrs. Gilligan who answered this time. “And it was good for him he did. I’ve lost enough sleep through the miserable rascal and I was just ripe for a tussle.”

“I don’t blame him for running,” said Teddy, with a chuckle.

“But where did he go?” asked Laura again. “We were sure that we’d see something-goodness knows what-when we turned the corner of the room.”

“And all we saw was a-a large amount of nothing at all,” added Violet, wide-eyed.

“Perhaps,” suggested Ferd, with a chuckle, “the aeroplane we heard belonged to him-”

“A ghost’s aeroplane,” murmured Billie, smothering another hysterical chuckle.

“And when you girls came in he just soared skyward and went off in it.”

“It’s funny we never thought of that,” said Teddy scornfully.

“Well, I wish we could find out what it is,” sighed Billie, as they started upstairs again. “This staying awake all night isn’t very much fun.”

“But isn’t it strange,” asked Laura, stopping on the landing and looking back at them, “that both the piano and the motor should start again on the same night?”

“Yes, it is, rather,” said Chet, adding seriously: “I wonder if there could really be any connection between the two.”

“There’s no use wondering, that I can see,” said Mrs. Gilligan, preparing to send them off to their respective bedrooms. “I think the best thing we can do is not to notice them any more. Perhaps the ghosts will get tired, if they find they don’t worry us,” this last with a chuckle.

“Well, but they do worry us,” said Violet plaintively. “Every time I hear that piano, I just about die of fright.”

“Listen,” commanded Billie, and as they listened they heard it again! The ghost, or whatever it was, was surely making a joke of them that night!

As soon as the boys could recover from their surprise they tumbled down the stairs, tripping over each other in their hurry, while the girls followed more slowly.

But again the noise stopped abruptly, and when they entered the room there was nothing to be seen or heard.

“Say, this thing is making me mad!” cried Ferd, glaring at the old piano as though it were the offender. “I don’t mind meeting an honest-to-goodness ghost, but I’ll be hanged if I’ll let him laugh at me!”

“I don’t see how you’re going to help it,” said Teddy. “Come on, fellows, it’s pretty nearly morning, and we can decide then what we’ll do to catch Mr. Ghost. I’m so sleepy I’m apt to fall asleep on my feet.”

So they went upstairs again, feeling rather miserable and dragged out with excitement, and crawled into bed.

“If this thing keeps up much longer, I’ll just be a wreck, that’s all,” groaned Laura, and almost immediately she fell asleep.

After a little while of staring into the dark, Billie and Violet followed her example, and once more there was quiet in the old house.

Nothing more disturbed them, but they woke the next morning, tired and cross and with a decidedly “morning after” feeling.

“I don’t want to get up,” complained Violet, turning restlessly in bed and punching her pillow. “I can’t get more than one eye open.”

“Shall we send for the doctor?” asked Billie, regarding her sleepily. “That sounds like a serious complaint.”

“Humph, I don’t need a doctor,” grumbled Violet. “I can prescribe for my case better than he could. What I need is a rest cure.”

“So say we all of us,” echoed Laura sleepily. “I’m going to take another nap, girls, and if anybody dares to wake me up, I’ll throw my hair brush at them.”

“I’m going to get up,” decided Billie. “I’ll only get a headache lying here.”

“Well, I hope you enjoy yourself,” said Laura, and settled herself in a still more comfortable position.

While Billie was dressing the two girls fell asleep again, and as she turned to look at them she almost wished that she had followed their example.

“But I knew I couldn’t sleep,” she said, turning away, “and, besides, I’m getting very hungry.”

But when she started down the broad staircase she found that she was the only one stirring in the house, and a strange, lonesome feeling took possession of her.

“Ugh,” she cried, glancing about her distastefully, “it’s the gloomiest place I ever did see. I’ll be glad when we leave it. That is, I would be,” she added wistfully, “if only Chet and I were going with the others to boarding school.”

She wandered into the room where the old piano stood and looked at it musingly for a few minutes. Then suddenly a thought struck her, and she clapped her hands gleefully.

“I wonder-” she said, then, remembering an old rat trap that she had come across several days ago, ran into the pantry to get it. She baited it with a fresh piece of cheese and set it carefully on the piano.

“Now,” she said, standing back and regarding her work with satisfaction, “we shall see what we shall see!”