Leroy Brown, known to everyone as Encyclopedia, is an eighth-grade boy living in Idaville, USA. His father is the Chief of Police. Whenever Chief Brown comes across a mystery he cannot solve, he brings the facts home to discuss over dinner. Encyclopedia listens quietly and uses his vast knowledge, great memory, and sharp thinking to solve the case before the meal is over.
One evening, Chief Brown discusses the death of Tim Nolan. Five years earlier, Nolan and his friend Daniel Davenport were suspected of stealing one million dollars worth of jewellery from the Diamond Mart. However, the police never found the stolen goods. Before dying of a stroke, Nolan left a will giving his palm-tree nursery to Davenport. Attached to the will was a page from a desk calendar with Davenport's address and four strange words: "Nom Utes Sweden Hurts." Neither Chief Brown nor Mrs. Brown can understand what the strange message means.
Encyclopedia studies the clue and quickly figures out the secret code. Since the words are written on a desk calendar sheet, he realizes that they stand for the days of the week. Nolan simply removed the letters "d-a-y" from each day and rearranged the remaining letters into new words. Therefore, Monday became "Nom", Tuesday became "Utes", Wednesday became "Sweden", and Thursday became "Hurts".
Following this pattern, the unwritten fifth day of the week is Friday. Removing "d-a-y" from Friday leaves the letters that spell "Fir". Encyclopedia asks his father if there is a young fir tree growing in Nolan's palm-tree nursery. His father confirms that there is indeed one on the south side of the house. The police search the area and find the stolen jewellery buried in a large jug of earth under the fir tree. Thanks to Encyclopedia's brilliant mind, another difficult mystery is solved.