When reports of a mummy terrorizing the New Mouse City Museum flood the phone lines, Geronimo Stilton, editor-in-chief of the Rodent's Gazette, is on the job! Geronimo is certain there is a logical explanation to all this, seeks to debunk the theory and prove that there's no mummy. Will Geronimo get wrapped up in more than he can handle? Is he about to become ancient history? Is there something, or someone, really lurking in the shadows of the New Mouse City Museum?