D&D: Continue arguing with him
From Create Your Own Story
"I am thinking you don't see well. I am offering to help YOU with your problem. You don't negotiate up from there." you claim. You manage to resist your libido.
He stands up and look at you:"Hrmph. As long as nothing goes in or out of those sewer. For the rest I am not concerned. " he says. Classic coward and lazy lieutenant.
You swear to yourself and decide to take a different aproach: "Your job is on the line here. Imagine that whatever is down there causes major problem for the city. You'll be blamed..." you continue.
For a second, he seems to swear under his beard. He then looks at you with voracious grin: "Hrm. It is true, but I will still ask something out of you. If you do it, I will tell my men to let you in the sewer."