"We're not saying anything," Frank answered. "But if you want to buy what I have, this is your last chance to make an offer."

Wayne Jensen sat still, glaring at his visitors. "Okay," he said at last, "I'll give you fifty thousand for it."

"The stone's all yours," Frank said evenly as he pulled a large pebble from his pocket and flipped it at the wealthy yachtsman.

CHAPTER IX.

The Racer's Edge Anger flashed across the Texan's face. "Just what are you trying to prove with this stupid charade?" he snapped, hurling the worthless pebble overboard.

"We want to know why a man like you is so anxious to get hold of the Faith diamond, even as stolen property," Joe told him. "If you don't mind answering a few questions, we won't tell the police that you had us attacked and offered to buy the gem."

"You can't prove anything," Jensen replied hotly. "Now get off of this boat before I have to throw you off!"

"Certainly," Frank said. "It was a pleasure meeting you."

The boys climbed down the ladder into their dinghy, feeling like sitting ducks. They did not breathe easy until they had reached the pier and joined their friends.

"What happened out there?" Chet asked as he grabbed the painter from Joe and fastened it to a piling.

"Frank's quite a salesman," Joe said proudly. "He almost sold a piece of gravel for fifty thousand bucks."

"I just wanted Jensen to admit he was after the gem," the older Hardy said. "Now we have to figure out why."

Fritz gazed at the motor yacht gleaming in the pale moonlight. "It looks like your friend is making his getaway!"

They could hear the sound of the yacht's engines starting up, and two men were on the bow pulling up the anchor. In less than a minute, the sixty-foot cruiser was on its way out of the basin and into the Potomac River.

Upon returning to the dock house, Frank and Joe questioned the dock master as to where Jensen might be headed. The jolly man could tell them only that the yacht sometimes left for one or two days. He wasn't sure where it went, but it couldn't go far in that time.

"Has Jensen bought any charts lately?" Frank asked.

"I seem to recall that he has," the dock master answered, scratching his head. "I believe he bought several of the Potomac River and Chesapeake Bay area. He also got one of Baltimore Harbor."

Thanking the dock master for his help, the four youths returned to the emba.s.sy. They kept an eye out for the gray sedan that had followed Chet and Fritz earlier, but it was not in sight.

"Do you think the Rabbit was driving that Peugeot?" Chet asked once they were in the German Emba.s.sy.

"Either he was or someone else who's very interested in us," Frank replied. "I hope the amba.s.sador heard from Dad today. I'm getting edgy about this whole business."

But Amba.s.sador Kriegler still had not received any word from Fenton Hardy. Frank and Joe had a fitful night's sleep.

In the morning, Frank called Detective Barnes for further information on the diamond theft. The police detective told them that he would run a check on Wayne Jensen, and that as yet he had no substantial leads on the missing gem.

Then Frank contacted Sam Radley in Bayport, who reported that Dr. Ha.s.so Werner was a very well-known geologist who taught at a German university. He was a good family man, and his record was clean.

"Maybe Dr. Werner's team is on the level after all," Joe commented. "It could have been just plain coincidence that they were meeting in the museum on Tuesday."

Frank shook his head. "Too many coincidences are adding up. Werner has the initials H. W., he's German, and he was there that morning. On top of that, there's something too secretive about him and his party."

"And we still don't know where he is." Joe shrugged, seeing his brother's point. "We ought to pursue that clue we found on their blackboard. 'Low clay' just might lead us to the geologist. If Dad is in trouble, we shouldn't be wasting our time chasing the diamond."

"Unless the theft ties in with Dad's case," Frank pointed out. "It's also quite a coincidence the Faith diamond was stolen the same day we got here."

The blond sleuth nodded. "I just wish Dad would call to fill us in on some of this stuff and tell us he's okay. I'm also shaky about the Rabbit. We haven't had a bomb thrown at us for two days, and it makes me wonder whether he isn't cooking up something really nasty."

"It's possible," Frank said, trying to play down the thought. "But I have a feeling that the Rabbit's job is over. Even if he didn't blow us to bits, he diverted us from the case long enough for us to lose the scent."

"Let's sure hope so!" Chet piped in. "One more sign of that guy and I'm back in Bayport!"

Over breakfast, the amateur detectives decided to pay a visit to Meg Rutlidge in Baltimore. They borrowed Fritz's two motorcycles since he was using the car. The bikes were German-made, light and swift. In less than an hour the boys were in Baltimore, a major port for commerce on the Eastern Seaboard.

Meg Rutlidge lived in a townhouse in the center of the city. She was hesitant to talk to Frank and Joe, but at last convinced of their sincerity, she opened up.

"Yes, I've been trying to reclaim Arthur's diamond from the Smithsonian," the kindly, refined woman said.

"My brother had always promised me I would have it someday. Then his racehorses began performing poorly and that old superst.i.tion about the stone's power to bring bad luck came up."

"So Mr. Rutlidge changed his will, giving the diamond to the museum and protecting you from its so-called curse?" Frank guessed.

Meg nodded. "He told me when he changed the will that he was doing it for my own good. He said he was convinced the gem had some kind of evil power. The funny thing is, until that day he had always laughed at the superst.i.tion. He even had a young racehorse named after the diamond, just so he could dispel the myth."

"Your brother's butler told us about the horse," Joe said. "She's supposed to run her first major race in a couple of days."

"Yes, but Arthur won't be there," Meg said sadly. She sat silently in thought for a moment, then went on.

"In any case, I thought it was very strange that he had that change of heart over the diamond. He knew the gem had about as much supernatural powers as the kitchen sink. He couldn't have been in his right mind when he made out that new will."

"And that's why you made your case to reclaim the Faith diamond from the museum," Frank deduced.

"Yes," the woman answered softly. "Only now there's no diamond to reclaim. I hope you boys find the thief who took it."

"Did a man named Jensen ever offer to buy it?" Frank queried.

"Not that I know of," Meg Rutlidge said. "If an offer was made, Arthur didn't mention it to me."

"What about the museum curator, Mr. Boswell?" the older Hardy asked casually, but watched for her response to the name. "I hear that you and Arthur were both good friends of his."

"Arthur was and I still am," Meg replied, giving no sign of being jarred by the question. "Why do you want to know?"

The sleuths explained that they had a hunch the curator might know more about the diamond's theft than he let on. The fact that Arthur Rutlidge's accident left some peculiar questions of its own, and that he was a friend of Boswell's, might tie in with the case.

Meg stared out the window, distracted by a thought. "David Boswell phoned me this morning," she said at last. "It was just a social call. He apologized for the loss of the diamond, knowing how much I had wanted it back. We talked about it for a while. But I couldn't help thinking that there was something else he meant to tell me and didn't."

"Does he believe in the stone's curse?" Joe asked.

"No. He's even helped me in my case to reclaim the diamond," Meg said, leaning back in her chair with a sigh. "He was planning to testify on my behalf that Arthur must have been out of his mind when he changed the will."

Convinced that Rutlidge's sister knew nothing about the gem's disappearance, Frank and Joe thanked her and left. They mounted their motorcycles and drove down to the harbor to see if Jensen's ship was there.

The harbor was busy with traffic, but the large yacht wasn't among it.

The sleuths then made a stop at a special museum of horse racing, a small brick building near the harbor.

A collection of films was available to the public for viewing, and the brothers picked out one in which Rutlidge's entry had lost unexpectedly. In a small viewing room, they threaded the spool into a projector and turned out the lights.

By stopping the film, running it in reverse, and then forward again in slow motion, Frank and Joe could see that Rutlidge's horse seemed to break stride during the race just as it rounded the far turn.

"Look at the way its ears perk up just before it loses its pace," Joe said. He stopped the projector, freezing the animal's motion as it rounded the turn.

"It sure appears as if the horse sensed something that made it falter," Frank agreed. "Almost as if it was trained to react to a signal."

"You think someone conditioned it to lose?" Joe asked, finding his brother's idea hard to swallow.

"Let's just say it might be time to ask Rutlidge's trainer, Max, a few questions."

The boys returned the film, left the museum, and rode over the hilly country roads that led to the Rutlidge estate.

They were not far from the city, however, when Joe's bike developed engine trouble. He had to coast down a hill and pull into a service station.

"I'm a biker myself," the attendant told the Hardys as he stepped away from the gas pumps to inspect Joe's motorcycle. "Haven't seen any like these around here, though. I bet I can fix 'em anyway."

The lanky young man wheeled Joe's bike into the garage and brought out a set of tools he used on his own machine. "Are you guys on the way to the cliffs?" he asked.

"What cliffs?" Frank inquired.

"I take my bike there all the time," the young man said as he pointed with a wrench to a motorcycle in the corner of the garage. "Best hiking in the area.

Frank glanced at the bike. It was covered with yellowish mud. "Looks like you drive it hard," he observed. "That mud's pretty thick."

"It's not mud," the youth answered. "It's clay, yellow clay. You get that down at the cliffs."

Frank and Joe instantly had the same thought. Could the words "low clay" they had found on the geologist's blackboard have been what was left of "yellow clay?"

"These cliffs are made of yellow clay?" Frank asked to get the story straight.

The lanky gas station attendant looked up from his work. "They're called the Yellow Clay Cliffs."

"You didn't see a group of scientists down there recently, did you?" Joe asked. "They would be drilling the ground?"

"So that's what those guys were up to," the youth said, his interest showing. "Geologists, huh? I saw them working at the base of the cliffs just this morning!"

CHAPTER X.

Follow the Yellow Clay Road Frank and Joe decided to put off returning to the Rutlidge estate. While Joe helped to fix his motorcycle, the older Hardy made a phone call to Washington. Since the boys were still officially suspects in the diamond burglary, they had to make regular contact with the police to inform them of their whereabouts.

Barnes had dug up some material on Wayne Jensen and related his findings over the phone. Jensen had indeed made a fortune. But a great part of his earnings were either undoc.u.mented or suspect, and were centered around dealings with foreign concerns.

"Let's go," Joe called out as his brother returned from making the call. "My bike's humming like new."

He took a few laps around the pumps to make sure the engine was working properly, then waved to the station attendant and wheeled back on the road. Frank took off after him.

In time, the steep hills gave way to much lower and flatter terrain covered with thick underbrush.

Following the gas station attendant's directions, the two sleuths took a road that led down to the sh.o.r.es of the lower Potomac, where the river emptied into the wide Chesapeake Bay.

The road followed the river for a short while before the terrain began rising again. In moments, the boys found themselves on a narrow lane, cut high into the wall of the bluffs that towered above the water. The bluffs were jagged from erosion, and the road wound around them in sharp curves.

It continued rising until it reached the top of the bluffs, more than a hundred feet over the river and bay.

There, dense pine forest covered the land. Except for a few dirt lanes running into the woods, there were no signs of civilization in the area.

Taking it slowly along the dangerous terrain, the Hardys kept an eye out for the geologists. At one spot, the cliffs suddenly became a deep yellow hue. Now the brothers traveled over a hard clay surface, making traction considerably worse for, the motorcycle tires.

"That guy at the gas station has got to be some kind of daredevil to take his bike out here for kicks," Joe shouted above the noise of the engines.

"When this stuff gets wet, it must be especially treacherous," Frank called back.

Following the dangerous road for another mile, the sleuths came to a point where the yellow clay ended.

Beyond it, the ground once again became dirt brown.

"We must have missed them," Joe said, swinging his motorcycle around. "Let's take it slower this time."

The boys drove back and forth over the area of the bluffs marked by the yellowish clay, but they saw no sign of the geologists whom the gas station attendant had told them about.

Joe braked his bike and waited for his brother to catch up. The day was growing hot, and he used a rag from his back pocket to wipe his neck and forehead, grimy with-a combination of dirt and sweat.

"Do you think they've already packed up and left?" Frank asked as he pulled alongside Joe's motorcycle.

"I don't know," Joe responded. "Maybe we should try exploring some of those dirt paths leading back in the woods."

They started their bikes up again, heading toward the top of the bluffs.

Just then, a pickup truck came from around a corner in the road. Both boys swerved hard to avoid the oncoming vehicle.

"That's the geologists' truck," Joe yelled. The Hardys spun their bikes in a one-hundred-and-eighty-degree turn and started down the road after it.