The captive sleuth watched as Gay deftly arranged her hair like Nancy's. Then, with eyebrow pencil and other cosmetics, transformed her face. Nancy had to admit the resemblance was striking.

"Incidentally," said Gay, "thanks for the loan of your pink dress. Wish I could have kept the date with that handsome John McBride."

"Tell me, who was responsible for the message phoned to Anna?" Nancy asked.

"Bud. He's a good mimic," Gay bragged. "And our skin diver threw the spear at you when Frank signaled."

"Whose idea was it to place the time Bomb?"

"Mine," Gay replied. "But Gil put it in the cottage."

Gay now admitted that Bud's midget submarine was the object which had capsized the girls' canoe. He and Simon had been in the craft and were practicing a partial ascent as the girls pa.s.sed over it.

"That was really just an accident," Gay added.

Nancy's mind dwelled on the submarine. Was it also part of Bud's "sharp idea"? She could get no answer from Gay about this.

The actress did admit that the gang was responsible for breaking in and turning on the phonograph record, stealing the lilac tree, and digging the hole into which Hank had fallen. They had also caused the inn to quake by using a strong vibrating machine against the cellar wall, then running off with it before being detected.

All these things had been done, Gay said, to make Emily and d.i.c.k close the inn and keep Nancy and the others from detecting the gang's project until they were finished in this locale and could make a getaway to another spot. "We knew you were finding out too much," Gay told Nancy. "So we had to act fast. The trouble was, nothing made you get out!"

On a sudden hunch, Nancy queried, "Does this other project of yours have to do with the missing tools?"

Gay hesitated. "That's something you'll have to figure out."

Just then, the boat dipped sharply. Gay clutched her stomach. "Oh, I feel terrible!" she cried, her face a grayish green. "I think I'm sea-sick!"

The impersonator slumped into a bunk. Nancy's eyes darted around the cabin, trying to guess where the diamonds might be. Certainly not in any of the obvious places. Her glance lingered on a wall barometer. This would be an ideal spot if its back were hollow!

Then the cabin door opened and Gil entered. "What's the matter with you, Gay?" he said roughly. "C'mon. We're headin' for sh.o.r.e till this blows over and the fog lifts."

"Oh, leave me alone!" Gay said irritably. "I'm ill."

The next moment there was a crash and the sound of splintering wood. Nancy was hurled headlong across the cabin, and Gil and Gay were flung to the floor. They heard cries from outside and someone shouting, "About, Bud! About!"

Gil was the first to recover from the crash. He dashed out of the cabin. In a minute he was back with Simon.

"We struck a log!" Simon gasped. "We're sinking! And there's a fire in the engine!"

"Besides, some boat's approaching!" Gil added. "Might be a patrol. Frank and the others have jumped over. We're scramming too, in the sub."

"Get up, Gay!" Simon ordered.

But the former actress, chalk-white, seemed unable to move. Simon rushed over and yanked the actress to her feet.

"The diamonds!" Gay screeched. "We can't forget them!"

"We can't be caught with loot," Simon argued. "We'll skin-dive for the diamonds later." He glanced toward Nancy. "I'd better cut her loose."

The man groped in his pocket for a knife, but Gay stopped him. "Don't be a fool!" she hissed. "If she drowns, we can't be blamed. Good-by, Nancy Drew!"

The trio raced from the cabin. Nancy, bound and helpless, was left alone in the sinking ship.

CHAPTER XX.

Nancy's Citation UNTIL now, Nancy had not fully believed that her captors would let her perish. But she was left, bound hand and foot, aboard a sinking vessel!

Suddenly Nancy sniffed the acrid smell of smoke -the fire was spreading! She screamed for help until her throat was hoa.r.s.e. Then, about to faint, Nancy heard an answering shout, and the sound of a boat pulling up outside the porthole.

"Oh, thank goodness," she breathed fervently.

Shortly, two men in River Police Patrol uniforms hurried into the cabin. They quickly untied Nancy and carried her on deck. She saw that the fog had thinned and that the cruiser's stem was aflame. Desperately she tried to tell the men of the escaped gang, and what had happened.

"No time to talk now!" one of them urged.

The patrol boat stood near the bow of the cruiser, which was almost submerged. Nancy and the men quickly transferred to the other boat.

As the patrol craft pulled away, giant searchlights played over the surrounding waters. Captain Morgan, head of the patrol, came up beside Nancy in time to see the burning cruiser go under. Emily Willoughby's precious diamonds would soon be on the river bottom.

Nancy identified herself, and quickly explained about being taken prisoner and left in the sinking ship to drown. "You must capture the five men and Gay Moreau! Some of them are probably swimming to sh.o.r.e. The others went in the sub."

To her astonishment, the captain asked Nancy to look through a nearby porthole into a cabin where three men sat. "Recognize them?" he asked.

"Yes!" Nancy gasped. "Bud Mason, Frank, and the skin diver!"

Captain Morgan nodded. "We fished them out of the water just before rescuing you. They said they had jumped overboard after colliding with a fallen log-but nothing about any prisoner on the cruiser."

"Naturally!" said Nancy. "Hurry! You might still spot the sub if it hasn't submerged."

Captain Morgan looked dubious. Nevertheless, he barked an order. A high-beam searchlight was played over the water.

A moment later Nancy cried out, "Look!"

A shark-shaped object could be seen floating above water in the distance. Captain Morgan picked up binoculars.

"You're right, Miss Drew. It is a small sub!" he exclaimed. "Full speed ahead!"

Nancy waited tensely as the patrol craft pulled alongside the submarine. Gay, Gil, and Simon were inside it, with the hatch open.

Captain Morgan and his men gave the actress a startled look, then glanced at Nancy. The girl's heart sank. No wonder the men were confused! Gay still wore her Nancy Drew disguise!

"Gay Moreau has been impersonating me," explained Nancy, as the trio were helped aboard and towlines attached to the submarine. "She and the others are diamond thieves."

"This girl has been impersonating me for some time!" Gay snapped. "My name is Nancy Drew!"

The young sleuth started to protest, when Gay withdrew a wallet from the pocket of her dress. Nancy was dumfounded when Gay took out a driver's license and handed it to the captain.

"This license was issued to Miss Nancy Drew of River Heights," the captain said, frowning.

Nancy realized that Gil must have stolen the license when he planted the bomb in the cottage! Gay smiled triumphantly. "This girl is the thief! She was tied up because she sneaked aboard our boat and tried to steal jewelry from my luggage."

Nancy realized that the actress in desperation had cleverly reversed the situation to keep from being arrested. No one aboard could, or would, identify the real Nancy Drew. If the gang's stories were believed the six might be released. Nancy could be taken into custody.

"By the time my identification can be established, the others will have recovered the diamonds and escaped," she thought desperately.

Just then, a foghorn sounded and the group on board saw a searchlight sweeping across the water. Moments later, a second patrol launch came into view and pulled alongside.

Gay Moreau had pushed forward to stand in front of the young sleuth. At the same time, Nancy and she recognized Carson Drew standing at the railing beside John McBride and Lieutenant Brice. Also present was Chief McGinnis.

"Nancy!" Mr. Drew called. "Oh, Nancy, my dear, you're safe!"

Gay smiled and waved back. Then she edged furtively toward the stern, as if intending to jump overboard.

Nancy, meanwhile, had been expecting such a move. Unnoticed by Gay she had backed up several feet. The next moment, as the actress hurled herself toward the rail, Nancy tripped her. Gay went sprawling on the deck.

"That's one score evened," Nancy said firmly.

But Gay was still undaunted as Carson Drew walked across a plank and was about to step onto the deck of the other craft. She leaped to her feet. Shoving Nancy aside, she dashed toward Mr. Drew.

"Dad-I'm so glad to see you!" she cried, and was about to fling herself into his arms when Nancy intervened.

"No, Dad, it's a disguise!" she exclaimed, and grasped Gay by the arm. With her free hand, she rubbed off some of the actress's heavy make-up.

As Gay stood glaring balefully, her true looks were disclosed. Carson Drew said severely, "Well, Gay Moreau, justice is catching up with you again." Then he kissed his daughter.

All this time Simon had been pinned against the railing by several of the police. Now he made a desperate effort to jump overboard, but was instantly stopped. "Well, I guess we've had it, Gay," he said grimly.

Gay's features were contorted with rage. "Next time we'll set a better bomb for you, Nancy Drew!" she screamed.

"There'll be no next time!" Chief McGinnis spoke sternly, as the river police officers put handcuffs on Gay, Gil, and Simon.

Brief explanations were made to Captain Morgan, who led the chief and Lieutenant Brice to the cabin where the other three captives were being guarded. The officials spent some time interrogating them while Nancy talked to her father and John McBride, bringing them up to date on the recent happenings.

"Gay almost had me fooled, until we came on board," Carson Drew admitted.

Later, in the captain's quarters, the officials met with Carson Drew, Nancy, and John.

"Nancy, you deserve an explanation from me," said John. "I told you once that my Army work was confidential. Actually I've been working on a case while visiting at Lilac Inn."

John stated that he was in reality a major at an Army missile base. "Some top-secret electronics parts had been stolen from the base, and suspicion fell on Frank Logan, a sergeant in the Engineers' Corps, who had been dishonorably discharged not long before the theft. Nothing was ever proved, but my mission was to follow up on the man and determine his guilt or innocence beyond a doubt."

The major had obtained a clue that Frank was in the River Heights area and finally traced him to the vicinity of Benton. John decided that staying at Lilac Inn, owned by his friend d.i.c.k, would be a good cover-up.

"One day, near the river, I came upon a piece of an engineer's insigne from the same branch Frank was in. This gave me an idea that he was in the vicinity. When you and Helen mentioned the man with the crew cut," John explained, "and his not trying to rescue you, I thought he might be Frank. Yet I had no luck pinpointing his whereabouts. That is, until I heard certain tools useful to an engineer and d.i.c.k's jig saw were missing. And when you found the metal device in the lilac grove, Nancy, I recognized it as a stolen electronics part. That reaffirmed my suspicions that Frank was nearby."

Major McBride continued, "I also learned that electronics parts were being stolen from shops and factories in this region, and the thieves were using a different stolen car or truck each time for their getaway, then abandoning it."

He told Nancy that the red panel truck was one of the vehicles used and Chief McGinnis explained to Nancy about finding it in Dockville, along with books on navigation and skin diving.

Nancy learned that Gay had discovered the river shack's old cellar when visiting the inn as a child. While working for Mrs. Stonewell, Gay had told Bud and his pals about the place and they hatched the scheme for storing the stolen parts there.

Some of the electronics equipment, John disclosed, was being sold on the black market at a town a hundred miles down the Muskoka River. By stealing the diamonds, Gay and the crooks would have enough money to live lavishly for a while until ready to start their nefarious scheme again.

"Were they the ones who used my convertible and left it in the lane?" Nancy asked.

John replied Yes, but only to cause one more annoyance. The major now explained that he had received permission from his superiors to talk with the police. "A black-market operator who was arrested tipped us off that the crooks from whom he was buying parts might be in Benton last night to arrange for a final getaway."

John said he had returned to Lilac Inn that evening in time to meet Mr. Drew, Chief McGinnis, who had come along during his free hours because of his interest in Nancy, and Lieutenant Brice. The trooper had just received word over the police radio of the accident to the cruiser. This, together with the fact that Carl Bard had seen Nancy go toward the river, had given John the idea that the men should board a patrol boat and search the sinking cruiser.

"This certainly has been an involved and dangerous mystery," said Carson Drew.

"Yes, and Nancy deserves most of the credit for solving it," the State Police lieutenant spoke up.

Nancy chuckled. "Don't forget, we still have to find Emily's diamonds. John, how about a skin-diving search by daylight tomorrow?"

"With pleasure." John grinned.

Everyone at Lilac Inn was relieved and thankful to learn that Nancy was safe and that the mysteries had been cleared up. The following morning the Willoughbys, d.i.c.k, and Helen came along to witness the treasure-diving expedition.

A river patrol launch stood by as Nancy and John skin-dived to the bottom of the Muskoka River. After locating the sunken cruiser, the couple boarded it and entered the cabin where Nancy had been imprisoned. The sleuth went immediately to the wall and took down the barometer. To her disappointment, the diamonds were not secreted there.

John and Nancy looked in every conceivable hiding place, but found no clue. Nancy racked her brains, trying to imagine what spot Gay would have chosen. A sudden hunch came to her as she spotted the actress's make-up case.

Nancy opened it, and searched among the contents. She picked out two tubes of lipstick. Nancy removed the tops and gasped.

The tubes were choked with glittering diamonds!

John gave Nancy a congratulatory pat on her shoulder. The girl detective put the lipsticks into a pouch attached to her waist and the divers surfaced.

Emily was thrilled upon recovering her jewels and tears came to her eyes. d.i.c.k and Mrs. Willoughby could not praise Nancy enough.

John beamed at his skin-diving companion. "One of your best deductions, Nancy."

A little later that day John announced that a salvage crew had raised the cruiser. A stock of valuable electronics parts was found in the small hold, including those Frank Logan had stolen from the missile base. The gang had planned to sell many of them to an enemy agent.

A week later Nancy was honored at a colorful Army ceremony where she was presented with the Distinguished Civilian Service Medal for outstanding work.

"This is marvelous. Thank you!" she said.

When the young detective returned to Lilac Inn for a party on the eve of Emily's wedding, the bride-to-be gave her two attendants pins set with tiny diamonds. Nancy's was in the form of a lilac spray.

"I had this made especially so you'll never forget the mystery at Lilac Inn, Nancy." Emily smiled. "d.i.c.k and I will be forever grateful to you."