Ihad only been a detective for a few months when i was hired to investigate a very odd case. traveling across town, i soon found myself walking down a dim, dingy street, looking for the law offices of one “l. creighton, esq.” entering the office, a very calm, well-dressed gentleman warmly greeted us. i was surprised to find the office spacious, neat, and clean. somehow, i had expected to see a cramped, untidy, and dismal space. what did the detective expect to see in the offices of the accountant?

A cramped, untidy, and dismal space.

Explanation:

The dectective is narrating how he was investigating a case, his investigation lead him to a dark and dirty street. The surroundings already tell us that anything close to that place would probably be the same. Imagine yourself walking thorugh an ugly part of your city, you would expect that the things located there will have a similar aspect to the exterior one. In this case, the detective was surprised because he found a "spacious, neat, and clean" office that contrasted to the street.  

the answer is somber