Famous five- five on kirrin island again

Julian, Dick, Anne, and George planned to visit Kirrin Island for their school holidays, but George’s father, Uncle Quentin, is using the island to conduct secretive scientific experiments. George is frustrated with his idea, but agrees to lend her island to her father until he completes his experiment. Uncle Quentin is later kidnapped by villains wanting his secret formula for alternative energy. Uncle Quentin is held in a sub-sea tunnel, and it is up to the Five to rescue him. During the adventure, Timmy plays an essential part in rescuing Uncle Quentin from the kidnappers. The children befriend an artistic boy named Martin, whose guardian, Mr. Curton, is part of the gang trying to steal the secret formula. After the rescue Martin is admitted to an Art School and is free from his guardian. Everything ends happily.