"I think I'm making progress," Nancy told her friend. "I may not see you until tomorrow morn ing. Will you explain to everyone?"

"Of course." Emily then said happily that d.i.c.k had arrived. Her fiance had learned from the explosives expert that the cottage fire definitely had been caused by a time bomb. The police were still working on the case.

Nancy said good-by, and mentally rehea.r.s.ed her plan. "I've had sleuthing adventures before," she thought. "But this will be the first time I've impersonated a 'ghost'!"

CHAPTER XIII.

The Guard's Mistake WHEN Nancy confided to her father the idea of impersonating the ghostly woman in the lilac grove, Mr. Drew looked dubious.

"I think it's risky, Nancy. And also, how do you know any of the gang is going to see you?"

"I don't. I only hope so. But, Dad, if I'm convincing enough, someone may call me by her name, and I may learn to whom she was signaling, without raising suspicion."

Reluctantly Mr. Drew gave his consent. "If anything goes wrong, scream as loudly as you can."

"I will. But I intend to do a good acting job," Nancy a.s.sured her father.

Right after supper she went to the attic and opened a storage trunk. From it Nancy took out a white evening dress, long-sleeved and flowing. A further search disclosed a black wig she had once used at a costume party, and a transparent white scarf.

"Just the props I need," Nancy thought.

Returning to her room, Nancy tried on the hairpiece. To her satisfaction it completely hid her own hair. Next, she wired pocket-size flashlights to the cuff of each sleeve of the gown.

"These provide a glowing effect," she thought.

Nancy packed the wig and dress in her suitcase. Then she went downstairs and kissed her father and Hannah good-by.

"I wish you weren't going back to Lilac Inn," Hannah fretted.

"Now, Hannah," said Mr. Drew, "you know Nancy wouldn't give up any mystery until it's solved."

He then requested his daughter to telephone him the next morning. Nancy promised and left the house. She reached Benton at eight o'clock. Dusk was closing in, but it had to be considerably darker before Nancy could proceed to Lilac Inn.

She took a side road out of town. "Doris lives close to the inn," she recalled. "I'll drop in to see her." Presently she drove into a dirt lane leading to the Drakes' attractive white farmhouse.

She found Doris and her parents playing croquet on the front lawn. They greeted her cordially.

"About time you came to call," Doris scolded teasingly. "Nancy, any more news about your double?"

"Well, yes." Nancy smiled. "It's turned into quite a mystery, which I'm trying to solve."

"I understand. Detective at work," Doris guessed wisely.

Nancy then asked the Drakes if they knew a fisherman in the vicinity who wore his hair in a crew cut. They shook their heads.

"Does anyone own the dock between yours and the one at Lilac Inn?" Nancy questioned.

Mr. Drake replied that there was no house on the adjoining property. He understood the dock had been abandoned for years.

By the time Nancy took her leave and drew near the inn, it was dark. She decided to park in the apple orchard. As the girl detective got out of her car she felt raindrops. She took a plastic coat with attached hood from the trunk of her convertible and put it on. Then, carrying her suitcase, she dashed toward the inn.

When she reached it, Nancy circled the building cautiously, not wishing to be seen by anyone. The old inn was ablaze with lights. As Nancy approached the recreation room she heard dance music.

She crept up to the shrubbery and peered in. Helen and John were dancing, and Emily's partner was a young man of medium build with reddish-brown hair and a rather serious expression.

"That must be d.i.c.k," Nancy surmised. She observed that Maud, Mrs. Willoughby, and Mr. Daly were talking in a far corner of the room.

"I'm glad they are having fun," Nancy thought, continuing around the inn. There was no sign near the building of the guard her father had obtained. No doubt he was down near the river. Nancy walked to the guest cottages, hoping that one might not be locked. Nancy tried the doors and finally came to one that opened.

"Brrrr!" she shivered, stepping into the chilly, damp room. Nancy's eyes quickly became accustomed to the gloom. The place had no furniture but a chair. "I'll have plenty of time to get ready. The ghost won't be out until the inn is dark. I may as well rest and go over my act," she thought, and sat down on the chair. "I only hope my masquerade will bring results."

The time crept by slowly, but finally Nancy saw by the luminous dial of her watch that it was eleven-thirty. She looked out the window. The rain had stopped and a few stars twinkled above.

All the lights in the inn were out. She noticed that John's cottage, too, was in darkness. "That's funny. He must have come back, but I haven't heard any footsteps since I've been here," Nancy mused. "Wonder where he is."

She opened her suitcase and lifted out the dress and wig. She put them on and took a small flashlight from her handbag.

Cautiously the masquerader made her way to the lilac grove, taking care not to stumble over roots or twigs. As she drew near it, Nancy thought she heard the distant put-put of a motorboat. But the sound soon faded away.

An owl hooted nearby. The darkness beneath the overhanging trees seemed forbidding. Suddenly Nancy felt panicky, but resolutely she put aside her fears. She clicked on the small flashlights attached to her sleeves and walked toward the spot where Helen had been struck. Dramatically, Nancy waved her arms back and forth.

"I wonder if someone will reply," she thought.

At the same moment she heard a noise in the underbrush. A small animal darted across her path, followed by the crunch of footsteps. Quickly extinguishing her lights, Nancy ducked behind a tall lilac.

The girl's heart pounded. A figure in glowing white moved slowly toward her hiding place. At this moment the moon came out from behind a cloud, illuminating the grove.

Nancy gasped. The other girl was in a long trailing gown. But Nancy felt as though she were looking into a mirror. The young woman's face seemed identical to Nancy's and she wore her t.i.tian-blond hair in exactly the same fashion Nancy usually did.

"My impersonator!" Nancy cried out involuntarily.

The strange woman stopped abruptly. She scanned the area with her eyes. Nancy came to a sudden decision: she would meet her "twin" face to face!

"I only hope my masquerade will bring results"

Without hesitation Nancy clicked on her lights and darted from behind the bush. She confronted the other figure in white. The young woman gave a start of complete surprise upon seeing Nancy. Before either could say a word, heavy footsteps were heard approaching.

The strange girl turned and fled. The next instant Nancy's arm was seized by a man. "Let go of me!" she cried.

The man relaxed his grip and Nancy whirled around to face him. He was tall, husky, and wore slacks and a sports shirt.

"Who are you?" she asked.

"I'm a guard-Carl Bard."

"I'm Carson Drew's daughter, Nancy," she said quickly. "We must catch the young woman. She's an impostor and-"

She broke off. Carl Bard was staring at her in obvious disbelief. "I don't see anybody else, only you, miss. But Mr. Drew told me his daughter is blond."

In dismay, Nancy remembered the black wig she was wearing. "Oh-this is sort of a masquerade," she explained, s.n.a.t.c.hing off the wig and hiding it inside her sleeve. "I'm visiting at Lilac Inn, and I know that my father suggested you come here."

"True. But I heard Miss Willoughby say Nancy Drew wouldn't be returning tonight." The guard's tone was still suspicious. Again he gripped Nancy's arm. "You'd better come to the inn with me. We'll find out who you are."

Exasperated, Nancy cried out "You must believe me. There was another girl here! She escaped just before you saw me. She's a thief!"

The guard was adamant, and Nancy had no choice but to accompany him.

"My disguise certainly boomeranged," Nancy thought in disgust as she snapped off the flashlights in her sleeves.

When they reached the inn the guard rang the bell of the back door, which was closest. In a few minutes Emily and Maud appeared, both in robes and slippers.

"Mr. Bard! Is something wrong?" Emily asked, after flicking on the outside light.

"I found this young woman-" the guard began as he and Nancy stepped inside.

"Nancy Drew!" Emily exclaimed. "We didn't expect you until tomorrow!"

"And all dressed up, too. Been to a dance?" Maud asked curiously.

Nancy noticed that the social director wore full make-up. Had she really been in her room, or could Maud Potter have been the person Nancy's double was to meet in the grove? If so, Maud might have seen Nancy and returned to the inn before she was discovered!

Now Nancy flashed Emily a warning glance and answered, "Had an interesting date."

Emily caught on quickly. She turned to Carl Bard. "It's all right. This is Nancy Drew."

The guard nodded. "I'm convinced. But-"

Before he had a chance to say anything more, Nancy said with emphasis, "I'll explain everything later."

The man shrugged, said good night, and left.

"Did you have a good time this evening, Nancy?" asked Emily with a twinkle.

"I always do," Nancy replied airily, for Maud's benefit.

Just then a pleasant voice broke in, "Somebody arriving at this late hour?"

d.i.c.k Farnham came forward to join them. Emily smilingly introduced her fiance to Nancy, "I certainly appreciate all you've done to help us," d.i.c.k told Nancy. "It's a lucky thing you came to Lilac Inn."

"Now we'd all better get some rest," Emily said, and everyone agreed.

Nancy was first to reach the stairway. As she stepped up, her foot caught in the hem of her gown. She stumbled, and the black wig fell from her sleeve to the floor.

Maud glared at it. "Hm!" she said disdainfully. "Have you been up to some sleuthing trick?"

The secret of Nancy having masqueraded on the grounds was likely to be guessed by this busybody!

CHAPTER XIV.

Earthquake Scare "TIRED of being a blonde, Nancy?" Maud asked sarcastically. "Or are you the mysterious ghost of Lilac Inn?"

Emily, although at first surprised, sensed that Nancy had used the wig for a good reason. With a wink at d.i.c.k, she said, "Nonsense. I'll bet Nancy's date took her to a masquerade dance."

The young sleuth was grateful for Emily's quick thinking. Nancy waited for another outburst from Maud, but none came. Instead, the unpleasant woman said in a bored tone, "I think masquerades are so childish. Well, I'm going to bed." She said good night and went upstairs.

Nancy now turned to the engaged couple. "Are you both too tired to stay up a little longer?"

d.i.c.k grinned. "Not if I'm going to hear why one of Emily's pretty bridesmaids-to-be is masquerading as Cinderella. Tell me, Nancy, is it a new style to wear flashlights on your dress sleeves?"

"What!" Emily cried, and examined Nancy's sleeves. "Why, Nancy, what on earth have you been up to?"

"Can we talk some place where we won't be overheard?" Nancy requested. d.i.c.k led the way to his office.

Once inside, Nancy told of her sleuthing activities and experiences that day and night. "I'm glad you helped me along with that 'dance' story, Emily. Only Dad and the guard and you two know where I've been."

d.i.c.k spoke up earnestly, "You might be risking your life for us, Nancy. Lilac Inn isn't worth that."

Nancy set her jaw. "I must outwit my impersonator before she outwits me. And if I do, I'm positive I'll solve the mysteries of this place, too."

d.i.c.k nodded understandingly. He said Emily had told him of all the odd happenings at Lilac Inn.

"I also explained to d.i.c.k about my fear that Maud has some hold over Aunt Hazel," Emily said, adding that she hesitated to ask her aunt outright unless necessary.

"Of course," Nancy said. "Mrs. Willoughby is upset as it is."

Emily said grimly, "If I find out Maud is threatening my aunt, she'll regret it!"

The three young people started upstairs once more. On the way, Nancy asked if Mary Mason and the gardeners had brought references when they came to Lilac Inn.

"Why, yes," Emily answered. "But at the time, d.i.c.k and I were so busy with work here, we didn't check them until later. They seemed all right."

The trio said good night, and Nancy entered her room. Helen was sleeping soundly, and did not awaken. It seemed to the young sleuth that her own eyes had just closed when she was awakened by Helen calling her name frantically.

"Nancy! Nancy! Wake up! There's an earthquake!"

"What?" Nancy sat up in bed. As she did the startled girl noticed that her bed was indeed shaking slightly.