Phineas Hawkins and his brother Ferb work in their family's inn, but dream of exploring the sea. One day they discover a treasure map that leads to the long sought after Treasure Island. They tell the absent-minded Dr. Clyde, and he finances an expedition for Treasure Island. Apon boarding the boys are immediatly forced to become the cabin boys of the grumpy Captain Doofenshmirtz where they meet Isabella, Baljeet and Buford. However the children discover the captain and the crew scheme to get rid of them and the doctor so they can have the treasure for themselves.