Looking for a fanfic os sonic the hedgehog

I'm looking for a Sonic fanfic I read on AO3.

It starts with Eggman capturing Sonic, but then another human scientist appears. I think he either worked with Gerald Robotnik before or showed up on his own. The important thing is that he doesn’t see mobians as living beings, but as sexual objects

There’s a fight, and he ends up locking Eggman up. Then he uses Sonic for "experiments" (you know what I mean), hurting him badly, almost killing him, then healing him just to do it again.

Shadow is the one who finds them. First he finds Eggman locked up, then he hears screams coming from somewhere else. He goes there (without freeing Eggman yet) and finds the scientist with Sonic. He attacks the guy hard, rescues Sonic (who passes out), and then frees Eggman, who tells him the scientist’s name.

Apparently, the scientist had a past connected to Gerald Robotnik. Shadow was younger back then, and there were other failed experiments before him. The scientist used to do similar things, and Maria confronted him about it. He almost did something to her, so Gerald stopped working with him.

In the present, the scientist dies after Shadow beats him. Neither Eggman nor Shadow wanted to save him.

After Shadow takes Sonic home, Eggman gives him a liquid that the scientist had used before, which helped Sonic heal.

At the end, Shadow stays with Sonic to take care of him.

I think the fic was in English

Soooo, does anyone know the name or maybe a little hint to found it? I read it like, 1 month ago, so pleaseeee, I need it