Fifth-grader "Encyclopedia" Leroy Brown solves ten mysteries and, by putting the solutions at the back of the book, challenges the reader to do the same.
The solutions to ten mysteries solved by Leroy "Encyclopedia" Brown are given in a separate section challenging the reader to match wits with the ten-year-old mastermind of Idaville's war on crime.
Idaville's secret weapon against lawbreakers, ten-year-old Leroy "Encyclopedia" Brown, helps the police force solve ten new cases, the solutions to which are found in the back of the book.
Ten brief cases allow the reader to match wits with ten-year-old crime-buster, Encyclopedia Brown, as he investigates such cases as whether a diary of George Washington's mother is authentic, or if a UFO picture supposedly taken by the army is real.