"Cat-Flap" crams a lifetime of adventure and peril in to a week and a half of mayhem, which begins with 11 year old Oliver Crumble unwittingly transforming into the body of his pet cat Gus and ends with events that threaten the destruction of his home town, the lives of everyone he holds dear and the enslavement of the entire human race. When pieces of Heronymous Munt's Pentacle of Power are discovered on a construction site, the Pentacle's body-swapping mischief lets rip on the unsuspecting townsfolk of Tiverington. A crime-wave is unleashed, an evil menace looms large and with utter chaos...