The fourth book in the hilarious series from Roald Dahl Funny Prize winning author Philip Ardagh and illustrator of The Gruffalo, Axel Scheffler. Over the years, the Grunts have made more than a few enemies. But fortunately they're all safely behind bars. Or are they? There's been a prison break-out, and three of them are after REVENGE. It's time for the Grunts to go On the Run... This last book brings back some familiar faces from the series and solves a couple of mysteries too...