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 a legendary valley, and Geronimo isn't even sure it exists. Little does he know that getting there will be an adventure among geysers, volcanoes, and rivers of molten lava.

Translation of: Sei nella lava fino al collo, Stiltonùt!. "Based on an original idea by Elisabetta Dami"--Title page verso.