An orphaned teenage girl steals a ship while on a sailing trip in Scotland with other disadvantaged youngsters in order to search for the mythical treasure of Odysseus - a search her lost father began but failed to complete.
Susan, a 15 year old girl in care, is due to set sail on a two-week trip along with other disadvantaged youngsters. Susan, however, has other things than the trip on her mind. Her father, working from a book speculating that Odysseus sailed in Scottish waters and buried treasure on the Isle of Barra, began an investigation into the myth, but disappeared before it was complete.
Susan hopes to follow in his footsteps and find the treasure. Taking advantage of a port call at Tobermory, Susan persuades the other kids to help her seize control of the ship, tying loyal young bosun Campbell to the mast. After an adventure via; a whirlpool, a cave, sea creatures, the police, an underground cavern and an ancient burial ground, they find the treasure and Susan uncovers the story of her ancestors.