D&D: Knock them both out with a stun spell while they are helpless
From Create Your Own Story
As they least expect it, you unleash your magic. This spell is easy enough to cast without words or implement. You just have to touch your target and that requirement is pretty easy. The two thief's eye suddenly turns empty and they collapse in the corner. Since you have past the toll you can simply continue your way ahead.
D&D: Move on to the merchant's district and find the sewer entrance