There's a werewolf-type creature on the prowl and suspicion falls on Gnasher. Dennis has to prove his best pal's innocence as the full moon shines down on Beanotown...

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.