Harriet and Sebastian Wynter are the children of a pair of archeologist explorers who traveled throughout the Mediterranean. Their childhood was filled with adventure, education, and even occasional danger, and they grew up to be brave and resourceful. With their parents' deaths, however, they are raised to adulthood by their beloved aunt in London. To please their aunt, they try to fit in with London society, but their love for adventure is always just beneath the surface, ready to launch them into trouble.

Harriet Wynter is struggling to be a proper lady. She is successful, but she pays for it with frustration at her lack of freedom. When her brother goes off with some unknown stranger who claims to have a trunk that belonged to their late parents, she is irritated because he won't take her with him. But when he fails to return, she determines to rescue him, disguises herself as a boy, and sets off on the stage to follow his trail. Her resourcefulness will be tested as she faces kidnappers, smugglers, social ruin, and, most of all, love.

In a convivial evening with his best friends, Lord Ashurst drowns his sorrows with too much drink and passes out. His friends play a trick on him and set him, peacefully snoozing, on the next stage south. To his confusion, he ends up on a country road, without valet or horse or even a change of clothes, along with a young boy apparently running away from school. It doesn't take him long to discover the boy is actually a young lady, but he's captured by her courage and decides to help her find her brother. Harriet leads him on his first real adventure...