Silly Billy Swim Trunks is about 9 Year old Charlie Robinson, who lives in Chilverhave. Charlie's best friend is Dudley. The only spider in history to lose a leg playing rugby, replaced by a team of secret spiders who live at Daniel Craig's House. Charlie takes Dudley to Chilverhave Primary in his lunchbox, where he and old friends Robert, Nathan, Bethany and Molly meet Miss Merrick, the pen flinging Teacher with Tourettes. Together they endure the reign of super bully, Clarkie, who prowls the playground looking for his next victim. Unknown to the friends, Dudley has a plan for Clarkie. One by one he takes down his group with a series of 'unfortunate' incidents, saving the best for last. One freezing afternoon during a swimming lesson at the local pool, Billy Clarke's clothes go missing and he has to travel back to school on the coach in his Swimming Trunks.