|"The Secret Guardians"|
| Season 13, Episode 7b|
|Original Airdate:|| April 6, 2010|
February 22, 2010
April 28, 2009 
|Written by:||Guy Lancaster|
|Storyboard by:||Daniel Decelles|
"A Portrait of the Artist as a Young Tibble"
"Fernlets by Fern"
When Arthur, Binky, and Sue Ellen stumble upon a beautiful and private woodland oasis right by their homes, they vow to tell no one and keep it as their secret spot. Before long, however, they start to find evidence of human habitation.
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, the Arsubians, 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.
- The episode and title are parodies of The Secret Garden.