Rufus Sebbleford and his friends are looking forward to a school trip to the Mr Splendiferous Science Park unaware that the mad scientist is keeping a dangerous troll locked up in the grounds. The scientist's obsession with trolls causes further problems for the Super-Troll-Knobbly-Foot family who are trying desperately to pass as humans. Meanwhile, the stinky trolls of Gloopyglen Babblebrook begin digging a tunnel under the science park in search of a new bigger cave for their expanding bellies. Before long, the children find themselves trapped as the park becomes swamped with revolting trolls. Rufus, Bruno and Polly must come up with a plan before their classmates become troll food. A slimy, smelly, sausage-slinging adventure packed with mischief, troll traps and a really reckless wacky scientist.