Frank and Joe smiled wryly. "Aunt Gertrude," Frank replied, "we really don't know. But please try not to worry," he begged her and his mother. "You know that Dad and the two of us will be careful."
When Mr. Hardy came home a little later, his family told him about the threatening telephone
call. The boys, however, did not mention the arrow warning in the presence of their mother
and Aunt Gertrude.
They knew it would only add to their concern.
Mr. Hardy was as puzzled as his sons. "It's a funny thing," he said. "At this point it's impossible to tell which 'case' the person is referring to. If I knew, it might shed light on either one."
The detective grinned and changed the subject. "Right now, I want you all to come for a drive and have a look at the boys' surprise."
"Swell!" Frank and Joe exclaimed in unison.
While Aunt Gertrude and Mrs. Hardy were getting ready, Frank and Joe went out to the car
with their father. Quickly the boys related their afternoon's experience, concluding with the
arrow incident.
The detective looked grim. "Whoever is responsible for these warnings is certainly keeping close tabs on us."
Mr. Hardy and his sons speculated for a few minutes on the fact that the pedal found in front of the house apparently had belonged to Ken's bike.
"I think Joe and I should go back tonight to the place where we had the picnic," Frank told his father. "In the darkness we'll have a better chance to sleuth without being seen. And there might be some clue we missed this afternoon."
"I suppose you're right," agreed his father. "But be cautious."
As Aunt Gertrude and Mrs. Hardy came out of the house, conversation about the mystery
ceased.
Everyone climbed into the sedan and Mr. Hardy drove off. Frank and Joe, seated alongside him,
were in a state of rising suspense. Was the surprise the one thing they wanted most of all?
CHAPTER VIII
The Strange Mill Wheel
A FEW minutes later Mr. Hardy was driving along the Bayport waterfront.
"Is the surprise here, Dad?" Joe asked excitedly.
"That's right."
Mr. Hardy drove to a boathouse at the far end of the dock area and parked. He then invited the others to follow him. He walked to the door of a boathouse and unfastened the padlock.
Frank and Joe held their breaths as Mr. Hardy swung back the door. For a moment they stared
inside, speechless with delight. Finally Joe burst out, "Exactly what we had hoped for, Dad!" and put an arm affectionately around his father.
"What a beauty!" Frank exclaimed and wrung Mr. Hardy's hand.
Rocking between the piles lay a sleek, completely equipped motorboat. It nudged gently
against clean white fenders as the waves from the bay worked their way under the boathouse
door.
The boys' mother exclaimed in delight, and even Aunt Gertrude was duly impressed by the
handsome craft.
"This is the same model we saw at the boat show," Joe said admiringly. "I never thought we'd own one."
"She even has the name we picked out," Frank observed excitedly. "The Sleuth!"
Shiny brass letters were fitted on the bow of the boat, with the port of registry, Bayport,
underneath them.
Mr. Hardy and his wife beamed as their sons walked up and down, praising every detail of the
graceful new craft. It could seat six people comfortably. The polished fore and aft decks carried gleaming anchor fittings, and the rubbing strakes were painted white. The Sleuth seemed to be
waiting to be taken for a run!
"May we try her out now, Dad?" Joe asked.
"Of course. She's fueled up."
Aunt Gertrude shook her head. "The Sleuth's an attractive boat, all right. But don't you two start doing any crazy stunts in it," she cautioned her nephews. "And be back for supper."
When the adults had left, Frank and Joe climbed aboard and soon had the Sleuth gliding into
the bay.
The boys had no difficulty operating the motorboat. They had gained experience running their
friend Tony Prito's boat, the Napoli, which had similar controls.
Taking turns at the wheel, the brothers ran the boat up and down the bay. "Terrific!" Joe shouted.
Frank grinned. "Am I glad we stuck to our agreement with Dad, and saved up to help buy this!"
For some time the boys had been putting money toward a boat of their own into a special bank
account.
Mr. Hardy had promised that when the account reached a certain sum, he would make up the
necessary balance.
Now, as the Sleuth knifed through the water, Frank and Joe admired the way the stern sat
down in the water when the boat gathered speed. Joe was impressed with the turning circle
and the fact that no matter how sharp the twist, none of the spume sprayed into the cockpit.
"Wait until Tony and Chet see this!" Joe exclaimed, when they were pulling back toward the boathouse.
"Speaking of Tony-there he is," Frank said. Their dark-haired classmate was standing on the dock, shouting and waving to them.
Joe, who was at the wheel, brought the Sleuth neatly alongside. He turned off the engine as
Tony rushed up.
"Don't tell me this dreamboat is yours?" he demanded in amazement.
"Nothing but," Joe said proudly.
Tony and the brothers inspected the boat carefully, comparing her various features with the
Napoli, They lifted the battens from the Sleuth's cowling and admired the powerful motor
underneath.
"She's neat all right," said Tony. "But I'll still promise you a stiff race in the Napoli!"
"We'll take you up on it after the Sleuth's broken in," Joe returned, laughing.
Tony became serious. "Say, fellows, something happened today in connection with my dad's
business that I want to tell you about. Your mother said you were down here," he explained.
"What's up?" Frank asked.
Tony's father was a building contractor and also had a construction supply yard where Tony
worked during the summer. "Today I went to the bank, just before it closed, to deposit the cash and checks we took in this week," he said. "The teller discovered that one of the bills was a counterfeit!"
"A twenty-dollar bill?" Frank guessed.
"Yes. How'd you know?"
The Hardys related Chet's experience. Tony's dark brows drew together. "I'd like to get my hands on the guy making the stuff!" he said angrily.
"So would we!" Joe stated.
The Hardys learned that the head teller had told Tony he would make a report to the Bayport
police and turn the bill over to the Secret Service, "Did he explain how he could tell that the bill was a fake?" Frank asked.
"Yes," replied Tony, and from his description, the Hardys were sure that the bill had come from the same batch as the one passed to Chet.
"Think back, Tony," Frank urged. "Have you any idea who gave it to you-or your father?"
Tony looked doubtful. "Three days' trade-pretty hard to remember. Of course, we know most of the customers. I did ask Mike, our yardman, who helps with sales. He mentioned one
purchaser he didn't know."
Frank, eager for any possible lead, carefully questioned Tony. The Hardys learned that three
days before, just at closing time, a faded green panel truck had driven into the Prito supply
yard. "Mike remembers there were no markings on the truck-as if the name might have been
painted out."
"Who was in it?" Joe prompted.
"A young boy-about fourteen-was with the driver, Mike says they bought about fifty dollars'
worth of old bricks and lumber. The boy paid him in assorted bills. One was a twenty. Our other cash customers had given smaller bills."