The Secret of the Underground Valley
From Sonic Retro
| Sonic X episode #62|
"The Secret of the Underground Valley"
|Production no.: 062|
| Original airdate: March 20, 2005 (FR)|
November 12, 2005 (US)
The Secret of the Underground Canyon is the 10th episode in the second season, and the 62nd overall episode of Sonic X. In the English dub, it is known as An Underground Odyssey.
The episode opens with a flashback of Cosmo's past. On board her home ship, she and her sister visit her mother, who is a large, non-anthropomorphic tree. Cosmo's sister explains that their mother is the only one who remembers what their home planet was like, and that their mission to stop the Metarex is the only way they can atone for their sins. Soon after this, the Metarex attack them with Hell Ship.
Cosmo's attention returns to the present as her friends set out to find the next Chaos Emerald on a new planet. Cosmo is in a landing party with Tails and Knuckles, and they explore the ruins of a city. Tails and Cosmo get separated from Knuckles when Cosmo presses a hidden switch by mistake, causing them to fall into a ravine. Tails remains cheerful during their adventure, but Cosmo is wracked by guilt over leading the Metarex to steal the Planet Egg from Sonic's world and putting her new friends in danger. As Tails tries to dispel her doubts, a cloud of fireflies leads them to an underground city. It turns out to be a base full of snakeman-shaped Metarex, but Tails' scanner shows that the Chaos Emerald is inside, so they sneak in.
Inside, they find a room containing many Chaos Emeralds: one real one in a central capsule, and many fake ones surrounding it. Tails reasons that this must be where the fake Emerald from Planet Breezer was made, and accesses the computers for more information. Surprisingly, Cosmo is able to read the Metarex language. As they finish downloading the data, one of the Metarex attacks them. They shock it with a cable, grab the real Emerald, and flee the caves together. Just as the Metarex catch up with them, Sonic and the others arrive and defeat the Metarex easily.
Though Cosmo feels bad about tripping the switch that trapped her and Tails in the ravine, her friends remind her that this allowed them to get the Chaos Emerald back. Though things seem to have ended happily for them, Dark Oak says to himself that they have only taken the bait he left for them, and he will destroy them and Eggman when they bring the Emeralds together.