After talking to the Vekel the Man (thieves guild bartender) while trying to locate Esbern I noticed him continuing the conversation after we appeared to be done. "That man there, he was inquiring too!" I tried talking to him to no avail so I went into thief mode, rummaged through his pockets and found a note telling him to alert his superiors if he located "insert my name here". I thought, "Oh no you dih'int!" and ran past him and waited for him outside, leaving the secret door open. As soon as he appeared I fired an arrow into his forehead knocking him back through the opened secret door. I crouched and ran back down and closed the door before any guards could locate me and looted the rest of the poor sod's belongings then propped him up in a corner as a warning. Felt like a pretty bad-ass thief there I did.