What do you say that we meet up with Urien in the slum we're about to enter, then?  We can say that he had grown concern about the recent occurrences in Ebb and decided to check into the matter himself, having unluckily not become aware of the mayor's printed help-wanted advert.  He seems like a fairly smart guy, so it's not unreasonable to think that he'd find his way down here, following the advice of the locals as to where the central plumbing system lay.