Percy the Pirate is a magazine story.
On a hot day, Percy spots some pirates on the beach at Brendam Bay; it is the Fat Controller with Stephen and Bridget and their friends. Percy is puzzled, but soon finds out that the Fat Controller has organised a treasure hunt and the children have to find a buried chest full of chocolate coins. Percy wishes he could join in the fun. Unfortunately, Percy has lots of work to do.
At Brendam Docks, the trucks that Percy is heading towards to collect are growing hot and cross. They devise a devious plot to derail Percy. Just then, Percy puffs up to his train and is coupled up. As Percy puffs back down the line with the very troublesome trucks, the trucks start to bump Percy who protests, but the trucks just bump him harder.
Meanwhile, on the beach, the children are also getting hot and cross; they have dug multiple holes in the sand but have found no treasure. In the end, the children give up and Bridget asks her grandfather where the chest is. The Fat Controller does not know where the chest is as he had asked a guard, who is now on holiday, to bury it.
Just then, Percy comes speeding around the bend on the track just above the beach. The trucks push Percy so hard that his brakes fail and he plunges off the railway and onto an empty stretch of beach. Luckily, the soft sand prevents Percy from getting hurt, but he makes a huge hole and gets stuck. The Fat Controller calls for Harvey who soon arrives at the scene. As Percy is hoisted out of the hole, Stephen lets out a call of delight. There is a chest at the bottom of the hole; Percy has found the hidden treasure. The Fat Controller is so pleased that he orders Harvey to take the trucks back to the docks and gives Percy the rest of the day off.
Soon, a picnic cloth has been tied around Percy's funnel making him look like a pirate. Then, he joined in the fun as the children shared out their treasure and call out "Three cheers for Percy the Pirate".