The stories follow the events that unfold over the few days before Halloween as the creative brother and sister prepare for their annual Fairy Ball.

Part One:"The Thinning of the Veils" While Martin and Sylvia wait for the invitations to arrive for their annual Halloween Fairy Ball, Sylvia spies something curious sticking out of the toy shelf in their bedroom. She examines it, and finds that it is an orange piece of paper with a drawing — and on the drawing is a red “X.” Martin declares that it must be a treasure map! And thus brother and sister are launched on a cross-town treasure hunt. Where will it lead them?