Eye Spy

The Lost Planet is the 22nd episode in the second season, and the 74th overall episode of Sonic X. In the English dub, it is known as Eye Spy.

Summary

After Cosmo discovered she has a codename White Seed and the Metarex are monitoring what she hears and sees, her amulet is shining and Cosmo screams. Due of this situation, The Blue Typhoon is transported to the deserted planet. Sonic and Chris are finally recovered from being almost killed by Shadow in the previous episode.

When the team discovers that Cosmo's brain is emitting a signal to the Metarex, they plan on trying to eliminate the signal, except that the signal is connected to the part of her brain that translates sounds and sight. While Miles "Tails" Prower and Cosmo are torn about this, Knuckles pushes for the surgery.

Meanwhile, Amy starts searching for Sonic (as always), but ends up bumping into Rouge. They both discover that this planet is not only Cosmo's homeworld, but the Metarex's as well. They also discover that Cosmo's people were able to transform into huge dinosaur-like beings to protect their planet from an alien invasion. However, a few of them wanted to be able to completely destroy the alien hoard, and so crystallized the Planet Egg in order to keep the transformation from sapping their energy. They eventually led to the abandonment of the planet and transformed into the Metarex.

Cosmo, horrified by the fact that the Metarex are using her to spy on them, intends to leave, but Tails reassures her that they all will help her defeat the Metarex. Sonic and the rest of the gang also support the new resolution, and they all are ready for an attack on the Metarex, maybe the last attack.

At the end of the episode, Bokkun arrives, telling Shadow and Chris that Dr. Eggman has been captured by the Metarex.