When Dick Wolf took over from Michael Mann, the show took on real life themes for the episodes and got away from the previous drug dealing storylines of Seasons 1 and 2. On the same token however, the show under Wolf arguably became darker,dreary, and very depressing. Perhaps, the changes that Dick Wolf made on third and fourth seasons made sense in portraying how the undercover job with all those shootings and stuff took its toll on the lives of everyone involved.