Harriet and Khuwelsa Edgbaston are not typical sisters.
Harry wants to fly but even with all her sister's ingenuity they can't build a flying machine. Instead they just have the steam-powered runabout Sellie built.
When they take a trip into Mombasa they are side-tracked by a landing Zeppelin and from that point things go from ordinary to outrageous.
As chaos reigns they are forced to make a decision that will change their entire future.