Shanghai, 1920: Doug and Becca MacKenzie meet their new guardian, their uncle Richard, for the first time. Their new home is to be his ship The Expedient, an oceanographic research vessel. As they explore the ship they become aware that it has hidden areas. They also suspect their uncle may be more than a ships captain. And what is the mysterious HGS?

This book is a good old fashioned adventure story, with heroes, villians, secret societies and pirates. I really enjoyed it.

The book has a slightly unusual layout, as it contains cuttings, diary excerpts and drawings from historical dossiers chronicling Doug and Beccy's adventures. These add another layer of interest to the story.