Replying...
Intro. In this story, Sonic and Shadow were infected by a small creature related to black doom. Who is supposed to be dead today and so you think. That little creature is still a little unknown but as far as is known it can control the individual AND cause it to lose the memory of what happened, without being able to remember what it did. Shadow after having fallen into the cave where he found that creature that controlled him, was taken medical assistance after having a contusion since before the fall he had hit his head. He found his right hand in blood in the woods, thinking it might be Rogue's. Sonic was also there covered in the blood of an unknown individual. After G.U.N found them, Shadows turned them in along with Sonic thinking they were dangerous. Sonic could not accept the reality doubt of knowing that he could kill his best friend Tails. They were then placed in containment cells.

Sonic infested

@Luna