Isidora Gizard, unhappy with her dull village life, decides to steal a motorbike and head for Paris. But the discovery of a dark family secret and a boy in trouble instead catapults her into a search for the doorway to a lost magical world. Now the children are drawn into a terrible struggle in which this beautiful world and all the creatures in it will disappear forever if they can't open the door in time. As they charge into danger, Isidora must confront the shocking truth about herself: that she alone holds the key.