chubby face was split with a wide grin.
'Get a load of this!' He showed them a badge with his picture on it. 'I'll have to wear it when I start work. Everybody has to wear one before he can get into the plant,' he added. 'Even the president of Elekton!'
Suddenly Chet became aware of Ken Blake, 'Hello!' the plump boy greeted him in surprise. Ken smiled, and the Hardys told their friend of the morning's adventure.
'Boy!' Chet exclaimed. 'Things are starting to pop! So you found that green truck!'
At these words a strange look crossed Frank's face.
'Chet,' he said excitedly, 'did you say everybody must show identification to enter Elekton's grounds?'
'Yes-everybody,' Chet answered positively.
'What are you getting at, Frank?' his brother asked quickly.
'Before yesterday's explosion, when we saw the gate guard admit the green truck, the driver didn't stop- didn't show any identification at all!'
'That's true!' Joe exclaimed. ''Mr. Markel doesn't seem to be the careless type, though.'
'I know,' Frank went on. 'If the green truck was sneaking in explosives-what better way than to let the driver zip right through.'
Joe stared at his brother. 'You mean Markel deliberately let the truck go by? That he's in league with the saboteurs, or the counterfeiters, or both?'
As the others listened in astonishment, Frank replied, 'I have more than a hunch he is-and Docker, too. It would explain a lot.'
Joe nodded in growing comprehension. 'It sure would!'
'How?' demanded Chet.
Joe took up the line of deduction. 'Markel himself told Ken the envelopes were for the printer.
Why did Docker say Ken wasn't at the mill the day I saw him? And what was the real reason for
his being discharged?'
'I'm getting it,' Chet interjected. 'Those men were trying to keep you from questioning Ken.
Why?'
'Perhaps because of what Ken could tell us, if we happened to ask him about the envelopes he delivered,' Joe replied. Then he asked Ken if Markel and Docker knew that Joe had picked up the envelope the day of the near accident.
'I didn't say anything about that,' Ken replied. The boy's face wore a perplexed, worried look.
'You mean Mr. Docker and Mr. Markel might be-crooks! They didn't act that way.'
'I agree,' Frank said. 'And we still have no proof. We'll see if we can find someone way or another.'
The Hardys reflected on the other mysterious happenings. 'The green truck,' Frank said, 'could belong to the gatehouse men, since it seems to be used for whatever their scheme is, and they
are hiding it at the deserted farmhouse.'
'Also,' Joe put in, 'if Victor Peters is the 'old man,' he's probably an accomplice.'
'And,' Frank continued, 'don't forget that the bike Ken used was available to both Docker and Markel to deliver the warning note. The arrow shooting occurred near the mill; the attack on us in the woods that night was near the mill. The warning note found in Chet's car was put there
after Markel told him to go to the front gate. The guard probably lied to Chet the first day we went to the mill-he never did phone the personnel department.'
'Another thing,' Joe pointed out. 'Both men are more free to come and go than someone working in the plant.'
There was silence while the Hardys concentrated on what their next move should be.
'No doubt about it,' Frank said finally. 'Everything seems to point toward the mill as the place to find the answers.'
'And the only way to be sure,' Joe added, 'is to go and find out ourselves. How about tonight?'
Frank and Chet agreed, and the boys decided to wait until it was fairly dark. 'I'll call Tony and see if he can go with us,' Frank said. 'We'll need his help.'
Tony was eager to accompany the trio. 'Sounds as if you're hitting pay dirt in the mystery,' he remarked when Frank had brought him up to date.
'We hope so.'
Later, Joe outlined a plan whereby they might ascertain if Peters was an accomplice of Docker
and Markel, and at the same time make it possible for them to get into the mill.
'Swell idea,' Frank said approvingly. 'Better brush up on your voice-disguising technique!'
Joe grinned. 'Ill practice.'
Just before supper Mr. Hardy phoned to say he would not be home until later that night.
'Making progress, Dad?' asked Frank, who had taken the call.
'Could be, son,' the detective replied. 'That's why I'll be delayed. Tell your mother and Gertrude not to worry.'
'Okay. And, Dad-Joe and I will be doing some sleuthing tonight to try out a few new ideas we have.'
'Fine. But watch your step!'
About eight-thirty that evening Chet and Tony pulled up to the Hardy home in the Queen.
Ken Blake went with the brothers to the door. 'See you later, Ken,' Frank said, and Joe added,
'I know you'd like to come along, but we don't want you taking any unnecessary risks.'
The younger boy looked wistful. 'I wish I could do something to help you fellows.'
'There is a way you can help,' Frank told him.
At that moment Mrs. Hardy and Aunt Gertrude came into the hall. Quickly Frank drew Ken
aside and whispered something to him.
CHAPTER XVII
Secret Signal
WITH rising excitement, Frank, Joe, Chet, and Tony drove off through the dusk toward the old
mill.
Chet came to a stop about one hundred yards from the beginning of the dirt road leading to the gatehouse. He and Tony jumped out. They waved to the Hardys, then disappeared into the
woods.
Joe took the wheel of the jalopy. 'Now, part two of our plan. I hope it works.'
The brothers quickly rode to the service station where they had been that morning. Joe parked
and hurried to the outdoor telephone booth nearby. From his pocket he took a slip of paper on
which Ken had jotted down the night telephone number of the Elekton gatehouse.
Joe dialed the number, then covered the mouthpiece with his handkerchief to muffle his voice.
A familiar voice answered, 'Gatehouse. Markel speaking.'
Joe said tersely, 'Peters speaking. Something has gone wrong. Both of you meet me outside the Parker Building. Make it snappy!' Then he hung up.
When Joe returned to the Queen, Frank had turned it around and they were ready to go. They
sped back toward the mill and in about ten minutes had the jalopy parked out of sight in the
shadows of the trees where the dirt road joined the paved one.
The brothers, keeping out of sight among the trees, ran to join Chet and Tony who were waiting behind a large oak near the edge of the gatehouse grounds.
'It worked!' Tony reported excitedly. 'About fifteen minutes ago the lights in the mill went out, and Markel and Docker left in a hurry.'
'On foot?' Joe asked.
'Yes.'
'Good. If they have to take a bus or cab to town, it'll give us more time,' Frank said.
Tony and Chet were given instructions about keeping watch outside while the Hardys inspected
the mill.
