Gnasher accidentally gulps down Dennis' permission slip for the school trip! There's only one thing for it - they need Prof von Screwtop to use his shrink ray to shrink them down to bite-size humans so they can travel on a sausage into Gnasher's tummy and find the slip! Easy! Well it would be if it wasn't for the tiny alien empress Miasma living in there.

The class dig up a mysterious time capsule which sets them off on a race to find hidden treasure before Walter or a greed-crazed Paul the Potato can find it first.