Brenda inherits the Mammoth Inn, a decrepit mammoth-powered hotel, from her deceased Aunt Maude. When Frank and Olive arrive to collect their inheritance, Brenda enlists their help and the Inventor to repair the inn and modernize it with devices such as metal detectors, security cameras and smoke alarms. However, when a wealthy businessman expresses interest in buying the inn, but only if mammoths are present and the inn is not modernized, Pilbeam struggles to hide the machines. Topics covered: smoke alarms, metal detectors, lasers, escalators, sensors, counterweights, infra-red.