The Secret Guardians

The Secret Guardians is the second half of the 7th episode of Season 13. It first aired on April 6, 2010 with The Portrait of the Artist as a Young Tibble.

Summary
Arthur, Binky, and Sue Ellen find a woodland oasis near their homes and vow to keep the area a secret. Soon they start to find evidence of human habitation and wonder if they've discovered an ancient civilization.

Plot
Sue Ellen and Arthur go down to the brook to test a model boat that Sue Ellen made, they run into Binky and the trio launches the boat but loose control of it and follow it down the river and stumbled into a paradise like enclave of the woods that they name arsubia and swear on a rock to keep it secret from the world. For Arthur and Sue Ellen keeping arsubia a secret from the world is hard because Sue Ellen discovers a few arrow heads and suspects that a lost civilization occupied the area. Arthur finds it hard to keep arsubia a secret because he hates keeping secrets from Buster. Binky takes it upon himself to enforce arsubia's secrecy, adopting a vigilante approach and requiring passports upon entrance. Eventually the trio stumble upon Buster, who informs them "arsubia" is actually "Baxteronia" a place Buster discovered with his dad since he was four. The episode ends when a sudden rainstorm starts and buster tells them to take shelter in a cave located in the enclave.