It introduces the main characters, Jack and Annie, who use a magical tree house belonging to the librarian Morgan le Fay to travel through time and space. Currently, Jack and Annie are on a quest to find four "M" things to break a spell on Morgan, having already found a moonstone and a mango. The core of the excerpt details their perilous journey to the Ice Age, where they encounter Cro-Magnons, narrowly escape a cave bear, and are eventually saved from a sabertooth tiger by a sorcerer and a woolly mammoth named Lulu, leading to the discovery of the third item: a mammoth bone flute.