It's 1851. Queen Victoria has once again called Lord Parker Greene into service, this time to discover how and why her flying mail schooners have been disappearing. While Greene chases the sky pirates, his niece and nephew, Mildred and Cole, his wards since their father disappeared, are coming of age in bucolic Wickwillowshire without much supervision beyond the staff at Wickwillow Manor. Parker and his missing brother, Cecil, under the guise of being Plant Hunters, travel the world as Queen Victoria's emissaries. They right the wrongs that allow England to remain powerful and a wonderful place to live, even while the rest of the world falls into squander. This time, the battle is against the sky pirates who have been stealing the flying mail schooners. The mail currently contains plans for new steam operated objects and devices-the pirates want to obtain these plans to use them against England. Back at home, Mildred and Cole find love with the arrival of the new Vicar and his two children.