The Big Dip — Melanie Jackson

Joe and his friend Skip are enjoying the thrill of the Big Dip, a famous rollercoaster, until they learn the old man in front of them has been shot. The old man mutters with his dying breath something about getting a Margaret Rose to the police. Joe leaves the crime scene to get on with his life. But someone is desperate for the Margaret Rose and thinks Joe has it. When his sister is kidnapped, Joe is in a race against time to solve the puzzle.