You've been sneaking around to get on the good side of the thieves guild for a good week or so, but you haven't been officially welcomed. To figure out why, you approach their leader, Mercer Frey

Only for him to immediately press the tip of a Dwarven dagger to your neck.

"You've been doing good for us. But I believe there's more under that stately plain face."

He nicks some of your skin with the dagger.

"So, start talking."