In Dull-on-Sea, Matilda's quiet life is suddenly turned upside-down by the arrival of an eccentric pirate family, the Jolley-Rogers. She quickly becomes friendly with them and Jim, their son, becomes her best mate.

In Dull-on-Sea, Matilda's quiet life is suddenly turned upside-down by the arrival of an eccentric pirate family, the Jolley-Rogers. She quickly becomes friendly with them and Jim, their son, becomes her best mate.

Jim discovers that he is a descendant from an expert on manners and he turns into a good-mannered boy. His good manners change when Matilda is captured. After giving Grandpa a feather pen, jealous Squawk, the parrot, thinks Grandpa got another bird and leaves.

Matilda, Max, and Alexia go on an adventure to find real treasure, but Jim tags along to collect the treasure himself. The three will have to find it first to make sure that it becomes their treasure! Brent is elected as class representative and makes being at school awful. Jim is ready to overthrow the dictatorship! After all, pirates only obey a good captain!

Jim takes Nugget on a "mermaid safari" to find a mermaid and has Matilda disguise herself as one. When Nugget finds out the truth, she makes them pay! The town is in panic when the Jolley-Rogers are mistaken to have the Pirate Black Fever because they are speaking gibberish.

Mrs. Bevan makes a new rule to banish all "signs of piracy." Jim and Matilda join her pirate "reform boot camp" and pretend that she has changed them. When the Pirate Code is inflicted on the Jolley-Rogers, the pirate family is left with no roof over their heads and the Winners move next door!