After the reader's parents are called out of the country on business, the reader is sent to live with their Aunt Fiona and Uncle Harvey in Fiskeville for the summer. The reader is especially disappointed to learn that they will have to spend the summer with their cousins Barney and Dora. Barney is a violent brute, and Dora is a brat.
Throughout the book, Barney and Dora are a nuisance to the reader, causing more trouble than good.
There are no endings where Barney and Dora disappear or die. In one ending, the reader acquires a giant lizard, and they intend on using it to protect themselves from their cousins. In one another ending, the reader uses a small portion of the chocolate cake to make themselves big enough to be able to defend themselves against Barney. In yet another ending, the reader switches bodies with Dr. Abbott, and they refuse to swap back until Dr. Abbott can create a formula capable of making Barney and Dora disappear; it is assumed that, until Dr. Abbott makes such a concoction, he will have to live with the reader's cousins.
Barney is a bully, and he's unafraid of beating up the reader. Dora is whiny, but she never intentionally tries to physically hurt the reader.
Barney has blond hair and a pudgy face. He is described as being much bigger than the reader. Dora is described as having hair that is dark, tied in braids, and long enough to hang over her shoulders.
- Barney and Dora each share a name with a popular children's show character. "Barney" is the name of the main character in Barney & Friends, and "Dora" is the name of the main character in Dora the Explorer.
- This refence is not present in the Portuguese adaptation of this book, as Barney's name is changed to 'Bernardo'.