Ok here's the deal. I retrieved the dagger from Embarl (talked it out of him) at the Sea Bounty Inn and I took it back to Mae'var, and he told me to go talk to Edwin to see if he had anything else for me to do. I did that but he suspected that I was spying on Mae'var and I got attacked by thieves. I killed all those guys, then I went to talk to Renal Bloodscalp in the guildhall but he say he couldn't go off the word of Embarl. Renal said he needed hard proof and that I should do some more investigation in the guildhall. I searched it upside down and inside out but found no proof, so I went back to talk to Mae'var but it says "He has nothing to say to you." What is the hard proof that Renal is looking for? I would appreciate any assistance you might be able to give me.

The dagger is the proof. Check to see if it's still in your item list. Cheers

The dagger is not the proof. Edwin has a key that opens a strongbox in Mae'var's rooms. There is a letter in the strongbox. That is the evidence.

As soon as Edwin suspected me of spying he disappeared or something and a bunch of shawdow thiefs appeared. I can't find anything resembling a key.

Nevermind I figured it out. I never did find the key that Edwin had, but I used the knock spell on the box and found the letter.

Edwin suspected you??
That's weird, when he found out, he told me he was also spying. Oh well.