Maltazard has tricked his way into the human world and his aim is simple: raise an army of giant seides and realise his evil ambition. Only Arthur (Freddie Highmore) seems able to thwart his plans, but first he has to get back to his bedroom and return to normal size! Stuck in tiny Minimoy size, Arthur and his friends will need all the help they can get in their final combat against Maltazard. Let the battle begin!