Death by whoopee cushion

"The best Halloween costumes. The funniest pranks. An endless supply of chocolate fudge that looks exactly like dog poo. Most kids would love it if their parents owned a joke store. But twelve-year-old Manya isn't like most kids. She's not interested in the cheap laughs at Pranks a Million. She loves science. She wants to save the world. The only thing she finds even vaguely interesting about her parents' shop is the science behind the pranks. After all, there's chemistry at work even in itching powder and stink bombs. Manya and her best friend Isaac are thrilled when their parents agree to sign them up for Serious Science, an after-school course. It's everything Manya has dreamed of: the class is fascinating, and their teacher, Dr. C. Michaels, is both smart and charming. She can just about forget that her parents drive a bright yellow Volkswagen Beetle with a red clown nose on the hood and headlights that look like googly eyes. Maybe. But one day Manya comes back from their Serious Science class to see two police in the store. A trick cigar bought at Pranks a Million blew up in a customer's face and burnt off his eyebrows. Then there's a poisoning incident. And when a whoopee cushion explodes, actually killing an innocent bystander, things become very serious indeed: Manya's parents are arrested for murder. It's up to Manya to prove their innocence -- and she may have to use some of the science behind the pranks to do so"--