خرابکاری در نمایشگاه علمی (157) (معماهای بچه‌های واگن)

Jessie wants her science fair project to make a difference. So when she gets the chance to test a local creek for pollution, she can't wait to get started. But when things start going wrong with her experiment, Jessie and her siblings don't just have an experiment to investigate, they have a mystery to solve! "Wanting to create a science fair project that makes an actual difference, Jessie decides to test a local creek for pollutants before her experiments are sabotaged by suspicious accidents"-- Provided by publisher