Title: The robot's revenge
Description: The Hardy's invention, Roger the Lobber, an automatic tennis ball retrieval and return unit, has been stolen from the Teen Inventor's Club competition and then reappears without warning, transformed into a device of danger.
Subjects: Juvenile Mysteries, Juvenile Fiction, Children's 9-12 - Fiction - Mysteries / Detective, Children: Grades 4-6, Mysteries, Espionage, & Detective Stories, Juvenile Fiction / Action & Adventure, Mystery and detective stories, series:HardyBoys, collectionID:HBMS3, Children's fiction, Hardy boys (fictitious characters), fiction