Grace O'Malley is doing just fine taking care of her father and younger sister, Amy. She certainly doesn't want her cousin Fiona from Ireland to move in and take over. Grace has enough to worry about, what with Amy's diabetes and her own problems at school with her teacher.
But Fiona does arrive and tries hard to fit in with the family. It's still hard for Grace until the day Fiona shares her story of the brave pirate queen named Grace O'Malley. The tale makes her wonder: Does she have the great courage of the pirate queen?