"Your father will be along any time now, so stop building up gory pictures," George cut in. To get Nancy's mind off the matter, she added, "How about exploring Bald Head Cave this morning?"

"All right," Nancy agreed with forced cheer-fulness. "I wonder how we reach the place."

They learned from June that even at low tide the only safe approach to Bald Head Cave was by motorboat. When she realized the girls intended to go there, June warned them not to venture near the cave. Nancy a.s.sured her they would be careful. She and her friends left the house and rented a st.u.r.dy craft from a fisherman at a nearby boathouse.

Under Nancy's guidance the small boat put-putted slowly along the sh.o.r.e. Rising above the water, and stretching out for about two miles, were the colorful cliffs which had attracted artists from all parts of the country.

"I see a man up on that cliff with a telescope," George said, scowling. "He's looking at us. I hate people with telescopes. They have an unfair advantagel"

Nancy laughed as she steered nearer sh.o.r.e. "No doubt summer visitors are resented by the all-year inhabitants."

The man disappeared from view as the boat came into the shadow of the cliff.

"Look! The entrance to the cave!" George cried as they reached an indentation about half a mile from the ocean. "It's rather large."

"Let's just explore the outside," Bess suggested nervously.

Nancy smiled as she switched off the boat's motor, allowing the craft to drift closer to sh.o.r.e. "You know very well, Bess, we couldn't learn a thing without going inside the cave."

"Besides, the story must be exaggerated," George added. "I don't believe in ghosts."

Bess, whose gaze had been focused steadily on the cave entrance, suddenly gripped her cousin's arm.

"What is it?" George whispered.

For a moment Bess, badly shaken, could not speak. Then, with a trembling hand, she pointed toward the dark mouth of the cavern and said shakily:

"The ghost! I saw its white robe. It-it went back into the cave!"

Startled by Bess's words, Nancy and George gazed toward the cave entrance. They could see nothing but the dark opening framed by rocks and water.

"You must have imagined it, Bess," declared George. "There's no ghost-nothing white."

"Not now, but it was there!"

"What did it look like?" Nancy asked.

"I saw only a white blur. But then, ghosts aren't supposed to have a regular form."

"You probably mistook a sea gull for a ghost." George laughed.

Bess's lips drew into a thin, stubborn line. "It certainly was not a bird," she insisted. "But forget it. Even if that cave were inhabited by twenty ghosts, I know I couldn't talk you two out of exploring it!"

Nancy had no intention of venturing farther in a reckless manner. As the boat drifted closer, she studied the entrance to the cave and listened intently.

"Hear any warning bell?" George asked jokingly.

Nancy shook her head. The only sound was the roar of the ocean in the distance.

"What's your plan?" George inquired.

"The cave is quite wide and if the water is deep enough we can row the boat inside," Nancy replied. From the bottom of the craft she picked up the lead line and began to take soundings at the entranceway. "The water is nearly two feet deep here," she announced, measuring the wet section of the line. "Our boat can't go aground."

Using the oars, the girls cautiously rowed through the cave entrance into the dark interior. Nancy, who always carried a flashlight with her, swept its beam over the jagged stone walls. There was a natural ledge on one side, etched in the rock by erosion. The walls were damp, and the temperature much lower than on the sunny bay.

"It seems like a very ordinary cavern," commented George, relaxing. "No ghost. No bell. No water pouring out."

Nancy maneuvered the boat to the ledge and fastened the painter securely to a jagged piece of rock.

"What are you going to do?" Bess demanded.

"I want to walk along the ledge for a short distance. This cave may have an inner room. It's too dark to tell from here, and if we take the boat much farther, we may have difficulty getting out."

Bess was reluctant to leave the craft, but when she saw that George intended going with Nancy, she too climbed out on the ledge.

Nancy's roving flashlight cut dancing patterns on the water-stained walls as the three girls moved cautiously along the narrow ledge.

"I'm not going on!" Bess announced suddenly, turning and hurrying back toward the boat.

"Well, how about it, Nancy?" George inquired dubiously. "This place is-"

Her gaze was fixed on a portion of the ledge far back in the cave.

"The ghost!" she whispered tremulously. "I saw it just then-a figure in white!"

Nancy had observed nothing, but George's fear increased her own growing uneasiness.

"We'll go," Nancy agreed.

The two girls walked rapidly along the ledge toward the entrance. They had taken scarcely a dozen steps when a bell began to ring far back in the cave. Loud and full in tone, the pealing held a mournful note as if tolling for departed spirits.

Electrified by the sound, Nancy and George stopped suddenly. The same terrifying thought came to each of them.

"The warning bell Mrs. Chantrey told us about!" cried George. "It rings just before water rushes through the cave!"

Nancy seized her by the hand. "Come on!" she urged. "We must get out of herefastl"

"Listen!" George cried tensely. "That roaring sound! Hear it?"

Both girls froze to the spot, for the sound they heard was the mad rush of a great wall of water plunging toward them with the speed of an express train.

"Run!" screamed Nancy. "Run for your life!"

CHAPTER IV.

Nancy Vanishes