The Great Airport Mystery by Franklin W. Dixon Page B

laughed over Joe’s description of Chet’s encounter with Lieber and the chocolate milk.
    After dinner the brothers joined their father in his study. Frank was the first to tell his story, then Joe. Mr. Hardy listened with great interest.
    â€œYou say the man who knocked you down wore a mask?” he asked Frank.
    â€œYes! And if he was a ghost, he was a pretty solid one! By the way, Peterson has asked us to find the ghost! Shall we take his case?”
    Mr. Hardy thought for several seconds before answering. “Yes, take it. This so-called ghost seems to bob up a good deal. He’s worth pursuing.”
    The detective and his sons also agreed that the mysterious behavior of Zimm and Lieber could not be coincidence. It must be linked with the case, and the two were working together in some sinister plot.
    Mr. Hardy warned his sons that they should be extra careful. “If Zimm and Lieber are involved in the platinum thefts, and think you suspect them, they may make it sticky for you.”
    â€œWe’ll try not to flub again,” Frank promised.
    â€œWhat do you plan to do next?” their father inquired.
    â€œI’d like to drive out to Zimm’s house tomorrow’ morning,” Frank replied, “and investigate the area. We might be able to come up with a clue or two.”
    â€œGood idea. I’ll keep on investigating at Stanwide itself.”
    Early the next day Frank and Joe drove to Zimm’s house and cruised slowly past it. They saw that the garage, in which Zimm kept his car, was empty, and surmised that he had already left for work. The boys parked their car on the next block, then walked back toward the house. They tried to act nonchalant.
    â€œThat’s where I ran into the masked stranger,” Frank said, pointing. “You investigate that side of the house, and I’ll reconnoiter the grounds.”
    Frank scanned the premises carefully, inch by inch. He saw the area of ruffled grass where he and the masked stranger had tumbled in their struggle. Unfortunately, even his trained eyes failed to detect a single clue.
    As Frank continued the examination, his brother suddenly spotted something which startled him.
    â€œFor Pete’s sake!” Joe exclaimed.

CHAPTER X
    Startling Discoveries
    FRANK rushed over to Joe. His brother was staring at something in a flower bed. Frank glanced down and was astonished at what he saw. There, deeply impressed in the soft dirt, were two footprints.
    The instep of the right foot was narrower than that of the left. The prints appeared to be duplicates of those the boys had discovered in the concrete floor of the Stanwide hangar.
    Clint Hill’s footprints!
    â€œWhat do you make of it?” Joe asked his brother excitedly. “Could Clint Hill be alive?”
    â€œThe reports certainly don’t indicate it,” Frank replied. “But if he is, why would he be sneaking around like this?”
    â€œI wonder if the whole thing is a hoax,” Joe said. “Maybe Lance Peterson is using us to cover up a crooked deal he and Hill are involved in. They feel safe because they didn’t count on our picking up the footprint clue in the hangar. Someone tried hard to keep us from seeing the prints. Maybe it was Hill himself!”
    Puzzled, the boys decided to have another talk with Peterson. As they were about to leave, a window in the house was flung open, and a woman poked her head out.
    â€œWhat are you doing here?” she shouted.
    Startled, the boys looked up. “We wanted to see Mr. Zimm. Is he at home?” Frank replied coolly.
    â€œThen why didn’t you come to the door, instead of prowling around out there?” demanded the woman in a rasping, unpleasant tone. “I’m Mrs. Zimm. What do you want with my husband?”
    The Hardys realized that they could not reveal to Mrs. Zimm their reasons for being there. Perhaps she was in the plot with her husband! On the other hand, she