There was no choice for Joe but to swing the Sleuth into another wide, sweeping turn. It would have been foolhardy to enter the river at such speed, and Joe knew that under the
circumstances he needed lots of room to maneuver. The motorboat zoomed back into the
middle of the bay. It seemed to the boys that suddenly there was tar more traffic on the bay
than there had been before.
'Look out!' Chet yelled. Joe just missed a high-speed runabout.
He turned and twisted to avoid the small pleasure boats. The young pilot was more worried
about endangering these people than he was about colliding with the larger vessels, which
were commercial craft.
'Keep her as straight as you can!' Frank shouted to Joe. 'I'll take a look at the engine and see what I can do with it.'
Frank stood up and leaned forward to open the cowling in front of the dashboard, as the boat
leaped across the waves in the bay.
'Watch out!' Chet yelled, as Frank almost lost his balance.
Joe had made a sharp turn to avoid cutting in front of a rowboat containing a man and several
children.
Joe realized that the wash of the speeding Sleuth might upset it.
'If those people are thrown overboard,' he thought, 'we'll have to rescue them. But how?'
Fortunately,
the boat did not overturn.
Frank quickly lifted the cowling from the engine and stepped into the pit. He knew he could
open the fuel intake and siphon off the gas into the bay, but this would take too long.
'I'll have to stop the boat-right now!' he decided.
Frank reached down beside the roaring engine and pulled three wires away from the
distributor. Instantly the engine died, and Frank stood up just as Joe made another sharp turn to miss hitting a small outboard motorboat that had wandered across their path.
'Good night!' Chet cried out. 'That was a close one!'
Even with the Sleuth's reduction in speed, the other boat rocked violently back and forth as it was caught in the wash. Frank grasped the gunwale, ready to leap over the side and rescue the
man if his boat overturned.
But the smaller craft had been pulled around to face the wash. Though it bounced almost out of the water, the boat quickly resumed an even keel.
The lone man in it kept coming toward the Sleuth. As he drew alongside, he began to wave his
arms and shout at the boys.
'What's the matter with you young fools?' he yelled. 'You shouldn't be allowed to operate a boat until you learn how to run one.'
'We couldn't-' Joe started to say when the man interrupted.
'You should have more respect for other people's safety!'
Frank finally managed to explain. 'It was an accident. The throttle was jammed open. I had to pull the wires out of the distributor to stop her.'
By this time the outboard was close enough for its pilot to look over the Sleuth's side and into the engine housing where Frank was pointing at the distributor.
The man quickly calmed down. 'Sorry, boys,' he said. 'There are so many fools running around in high- powered boats these days, without knowing anything about the rules of navigation, I
just got good and mad at your performance.'
'I don't blame you, sir,' said Joe. Then he asked, 'Do you think you could tow us into the municipal dock so that we can have repairs made?'
'Glad to,' said the man.
At the dock, the Hardys and Chet watched while the serviceman checked the Sleuth to find out
the cause of the trouble. Presently he looked up at the boys with an odd expression.
'What's the trouble?' Frank asked. 'Serious?'
The mechanic's reply startled them. 'This is a new motorboat and no doubt was in tiptop
shape. But somebody tampered with the throttle!'
'What!' Joe demanded. 'Let's see!'
The serviceman pointed out where a cotter pin had been removed from the throttle group. And
the tension spring which opened and closed the valve had been replaced with a bar to hold the
throttle wide open, once it was pushed there.
The Hardys and Chet exchanged glances which meant: 'The unknown enemy again?'
The boys, however, did not mention their suspicions to the mechanic. Frank merely requested
him to make the necessary repairs on the Sleuth. Then the trio walked back to the Hardys'
boathouse.
Several fishermen were standing at a nearby wharf. Frank and Joe asked them if they had seen
anyone near the boathouse.
'No,' each one said.
The three boys inspected the boathouse. Frank scrutinized the hasp on the door. 'The Sleuth must have been tampered with while it was inside. Unless it was done last night while we were
unconscious.'
There was no sign of the lock having been forced open, but near the edge of the loose hasp
there were faint scratches.
'Look!' Joe pointed. 'Somebody tore the whole hasp off the door and then carefully put it back on.'
Frank looked grim. 'I'm sure this was done by the same person who attacked us last night, and sent us the warnings.'
'You're right,' said Joe. 'This is what Dad would call sinister tactics.'
Again both brothers wondered with which case their enemy was connected. There seemed to
be no answer to this tantalizing question which kept coming up again and again.
Chet drove the Queen back to the Hardys', and the brothers rode their motorcycles. When they
reached the house they went at once to the lab with the note Chet had found in his car.
They dusted it for fingerprints but were disappointed again. There was not one trace of a print.
The boys found, however, that the paper was the same as that used for the previous warnings.
'Well,' said Joe, 'I vote we go on out to the mill.'
The boys went in the Queen. Chet had just brought his car to a stop on the dirt road when Joe
called out, 'There's Ken Blake trimming the grass over by the millrace. Now's our chance to talk to him.'
The three jumped out. Ken looked up, stared for a second, then threw his clippers to the
ground. To the boys' surprise, he turned and ran away from them, along the stream.
'Wait!' Frank yelled.
Ken looked over his shoulder, but kept on running. Suddenly he tripped and stumbled. For a
moment the boy teetered on the bank of the rushing stream. The next instant he lost his
balance and fell headlong into the water!
At once the Hardys and Chet dashed to the water's edge. Horrified, they saw that the force of
the water was carrying the boy, obviously a poor swimmer, straight toward the plunging falls!
CHAPTER XII
An Interrupted Chase
FRANK, quick as lightning, dashed to the mill-stream and plunged in after Ken Blake. The boy
was being pulled relentlessly toward the waterfall. In another moment he would be swept over
the brink of the dam!
With strong strokes, Frank swam toward the struggling boy. Reaching out desperately, he
managed to grasp Ken's shirt.
Joe jumped in to assist Frank. The two boys were buffeted by the rushing water but between
