Piper is sad about leaving her home and friends behind when her father, a Navy aircraft mechanic, is transferred yet again, but with help from her often-annoying sisters and a surprise from their parents, she finds happiness in their new home in Pensacola, Florida.

While staying at the seaside, Catherine "Cat" Royal and her friends are captured and pressed into service in the British Navy and Cat, once again disguised as a boy, travels to the New World with survival her only goal.