Geronimo Stilton's ancient ancestor Geronimo Stiltonoot is back in another prehistoric adventure! Geronimo Stiltonoot and his family are off to find a cure for Grandma Ratrock's aches and pains. She's heard that a remedy hides in Cheesy-La, a legendary valley that Geronimo isn't even sure exists. Little does he know that getting there will be an adventure among geysers, volcanoes, and rivers of molten lava!