On an impulse, Penny buys back her old car, the Leaping Lena, even though she has a new car and no money, but fortunately, she gets another job at her father's newspaper. Penny discovers a strange silken ladder and learns how it is used in burglaries.
"Not to my knowledge," Louise answered. "If I were in your shoes I should worry about more serious matters than those connected with a mere silk ladder."
"The world is filled with serious things," sighed Penny. "But mystery! One doesn't run into it every day."
"You do," said Louise brutally. "If a stranger twitches his ears twice you immediately suspect him of villainy."
"Nevertheless, being of a suspicious nature won me a new car," Penny defended herself. "Don't forget Dad gave it to me for solving a mystery, for telling his newspaper readers what was going on Behind the Green Door."
"Oh, your curiosity has paid dividends," Louise admitted with a laugh. "Take for instance the time you trailed the Vanishing Houseboat, and again when you lowered the Kippenberg drawbridge to capture a boatload of crooks! Those were the days!"
"Why dwell in the past, Lou? Now take this affair of the silk ladder--"
"I'm afraid you'll have to take it," Louise