I have a question about this quest. Im in Summitmist Manor about to start this. I spoke to a few of the guests already. I haven't killed anyone yet. But Neville attacks me as soon as I try and speak to him. Just wondering why? I have zero bounty, not that that should matter. My infamy is quite high as I finished the entire Thieve's Guild chain. Again, not sure if that would matter. Any answers would be much appreciated. Thanks!

It's your high infamy. Infamy affects disposition of NPCs with high responsibility. Neville has both high responsibility and fairly high aggression. NPCs with high aggression will attack if their disposition drops enough. You are supposed to kill him anyway though so it just makes your job easier if he attacks you since you can then kill him in self defense and incur no bounty.