Encyclopedia Brown, Boy Detective

Ten-year-old Leroy Brown is known throughout his town of Idaville as "Encyclopedia" because of his vast knowledge of facts learned from books. His father is the town's chief of police. For nearly a year, no crime in Idaville has gone unsolved, a success secretly due to Encyclopedia, who solves his father's most difficult cases during their dinner conversations.

The first case involves a robbery at a men's shop. The owner, Mr. Dillon, claims he identified the thief as the notorious Natty Nat by his signature coat, even though the robber had forced him to face a wall. Encyclopedia points out that Dillon could not have seen the key detail on the coat's back. He concludes the owner invented the robbery to hide his own theft of money from his business partner.

Inspired by his mother's praise, Encyclopedia opens his own detective agency in the family garage, charging 25 cents per day plus expenses. His first client is a small boy named Clarence Smith, whose tent has been taken by a local boys' club, the Tigers, led by the tough Bugs Meany. Clarence says he set up the tent last week, before a two-day rainstorm began. Bugs claims Clarence stole it from the Tigers' clubhouse that morning. At the tent, Encyclopedia accidentally kicks over a pack of cards, scattering them on the ground inside. He observes that the cards and the ground are completely dry. He explains to Bugs that this proves the tent was erected before the rain started, confirming Clarence's story. Bugs and the Tigers retreat.

Next, a boy named Peter Clinton hires Encyclopedia to verify the authenticity of a Civil War sword Bugs Meany wants to trade for Peter's bicycle. Bugs claims the sword belonged to General Stonewall Jackson. An inscription on the blade reads, "To Thomas J. Jackson, for standing like a stone wall at the First Battle of Bull Run on July 21, 1861." Encyclopedia immediately identifies the sword as a fake. He points out two historical errors: Jackson's Southern troops would have called the battle Manassas, not Bull Run, and no one in 1861 would have called it the First Battle of Bull Run, as the second battle at that location did not occur until the following year.

A new girl in town, Sally Kimball, challenges Encyclopedia to a "battle of brains." She presents a mystery: The Great Merko, a famous trapeze artist, died in 1922, leaving a will that granted a fortune to the oldest grandson after 40 years. In 1962, a man named Fred Gibson claims the inheritance. A woman, Merko's grandniece, objects, truthfully stating that the Great Merko was not Fred Gibson's grandfather. Sally asks who gets the money. Encyclopedia solves the puzzle by explaining that the Great Merko was a woman, and therefore Fred Gibson's grandmother, making him the rightful heir.

Encyclopedia makes Sally his junior partner. While on their way to deposit the agency's earnings, they witness a bank robbery. The robber flees and collides with a blind beggar named "Blind Tom." Chief Brown catches a suspect, but the bag he carries contains only a loaf of bread. Encyclopedia and Sally investigate Blind Tom at his hotel and find his room door ajar. Inside, a reading lamp is on, illuminating a newspaper on the pillow. Encyclopedia realizes Blind Tom is not blind and that the collision was planned. The robber and the beggar switched bags, giving the robber the decoy bag with the bread. Chief Brown finds the stolen money in Blind Tom's room.

Later, the Princess Bake Shop is robbed, and an eyewitness identifies John Abbot, a man with a criminal record. Chief Brown and Encyclopedia go to question Abbot, who claims he just arrived after a 12-hour drive. During the questioning, Abbot's young, barefoot nephew climbs onto the hood of his car and plays happily. Encyclopedia tells his father that Abbot is lying. If the car had just completed a long drive, its hood would be extremely hot, and the barefoot child would have cried out in pain. The cool hood proves the car has been parked for a long time, invalidating Abbot's alibi.

Chief Brown is distressed after a valuable diamond necklace is stolen from a party guest, Miss Stark, while he was on guard. Miss Stark had felt ill and retired to a guest room, locking the door. Chief Brown stood outside and heard her scream, followed "a few seconds later" by two gunshots. He broke in to find her fainted and the necklace gone. Miss Stark later claims she did not see or hear any thief. Encyclopedia identifies the flaw in her story: she screamed before the shots were fired. He reasons that she would have had no cause for alarm until after hearing the gun, proving she staged the robbery. Police search her room and find the hidden necklace and gun.

A grocer, Mr. Patch, hires Encyclopedia after a break-in. The thief, a member of the Lions boys' club, fled, leaving his knife stuck deep in a watermelon. Mr. Patch accidentally wiped the fingerprints from the handle. Encyclopedia confronts four members of the Lions. While arguing his innocence, one boy, Corky, says, "Mine has a blade a half inch longer." Encyclopedia realizes this is a confession. Since the knife's blade is buried in the watermelon, its length is impossible to see. Corky could only know the length of the hidden blade if it was his own.

While Encyclopedia is at the dentist, Dr. Vivian Wilson, Sally's roller skates are stolen from the waiting room. Encyclopedia learns that the only other child in the medical building that morning was a boy named Billy Haggerty. When confronted, Billy denies being near Dr. Wilson's office and claims to have never heard of him. However, he gives himself away. By saying, "I had a sprained wrist, not a toothache," he reveals he knew Dr. Wilson was a dentist. He also refers to the doctor as "his," revealing he knew Dr. Wilson was a man, despite the feminine-sounding name Vivian. Caught, Billy returns the skates.

Finally, a group of boys hires Encyclopedia because a boy named Eddie Phelan always beats them at egg-spinning contests, winning their prized possessions. Encyclopedia recalls seeing Eddie in a drugstore earlier, where Eddie's spinning egg fell off a counter. The owner got a broom and dustpan to "sweep up the mess." Encyclopedia realizes this means the egg was hard-boiled, as a raw egg would require a mop. A hard-boiled egg spins much longer than a raw one. At the next contest, Encyclopedia challenges Eddie to switch eggs with his opponent. Eddie's refusal exposes his cheating method, and he is forced to return everything he won unfairly.