In The Circus of Adventure the kids are looking forward to a summer break now school is over and are soon off on holiday with Bill and Allie. But Sir George has asked Bill to protect the future Prince of Tauri-Hessia who subsequently joins the kids on holiday. Soon the family is thrown in to a daring adventure as they are pursued by the baddies who plan to overthrow the King and place a puppet Prince Tauri-Hessia on the throne.