[Steve has no idea in hell what's actually happening to Eddie but he's placed that responsibility upon himself. He doesn't even know where to begin when it comes to a cure, if thats even an option but he can't just allow whatever is happening to Eddie claim him. Steve wouldn't be able to forgive himself, not after all the horror Eddie has already endured. 

This isn't fair. ]

We can figure it out? There has to be a fucking answer, right?

[Right?

Steve is trying not to allow the worry and concern show on his face. The guilt that he's failed Eddie completely, that Steve couldn't actually save him from this. ]

I'm not just going to fucking leave you here alone, man. Can you even go outside like this?

[Typical Steve Harrington for you, the man that isn't going to leave a friend behind when in danger even when his friend is the danger.]