The six horrible Herdman children create mayhem during Halloween. Annotation. The Herdmans plus Halloween have always spelled disaster. Every year these six kids -- the worst in the history of Woodrow Wilson School, and possibly even the world -- wreak havoc on the whole town. They steal candy, spray-paint kids, and take anything that's not nailed down. Now the mayor has had it. He's decided to cancel Halloween. There won't be any Herdmans to contend...

Geronimo Stilton, editor of The Rodent's Gazette, goes on an investigative, underground adventure through New Mouse City to find a missing document.