Tim is thrilled when his parents allow his best friend, Biscuits, to come on holiday to Llanpistyll, Wales, with them. He and Biscuits are having an absolutely brilliant time eating ice cream, having picnics, and making sandcastles - until a deadly, fiendish enemy in the form of the bully Prickle-Head and his sidekick, Pinch-Face, arrive, and things begin to go wrong.

The bullies tease Tim, kick down his sandcastle, and pick on Biscuits, and before long Tim wonders whether it would be better to avoid the beach for a while and lie low. But Biscuits is determined to enjoy his holiday, and the chums soon find themselves in the middle of a dire and dangerous adventure. Luckily, help comes from a rather unexpected source and gives Tim the chance to become Super-Tim and save the day.