Enid Blyton

George, Julian, Dick, Ann and the dog Timmy, hunt for treasure in a shipwreck under the ocean, and in the Castle of Kirrin Island.

The five friends on vacation on an exotic island while diving in a shipwreck exploring around they found a mysterious compass, which is the indication of a pirate treasure, according to the local girl Joe. They find out that the Investor Mr. Haynes has plans to build a resort in the bay. Joes family would sold by these plans from the bay, and so they decide to look for the pirate treasure to save her home and her family..

The children Julian, Dick and Anne spend a summer holiday at the Kirrin Farm where their tombiyish cousin Georgina lives with her dog Tim and her parents. Georgina is being punished for her poor school performance, and her father hires a private teacher.

The four kids, Julian, Dick, Georgina and Anne plus the dog Tim go on a bike trip without any grownups around but they are soon followed by a another boy, Richard, who is pursued by kidnappers.

A country relocation leads cousins Julian, Dick, Anne and tomboy Georgina to unite and investigate mysterious happenings, thwarting a notorious drug smuggling operation with help from their dog Timmy. (imdb)