Amazingly, this already very good show seems to be better in its fourth season than ever before. It doesn't ever promise you a tidy conclusion. You get them for some cases, for some you don't. And the characters lives just go on: for example, Leo continues to deal with the deteriorating state of his wife, who has dementia. This isn't a major plot point: just a reminder that police men have lives outside of work, and that those lives often influence their behaviour. And we're reminded about this all the time in small ways. Another example stems from a case that I think was in the third season: some bones were found while excavating for the foundation of a new building. This has become an archaeological dig, with all the repercussions that go with that. One of their pathologists, Sunny, goes there periodically (although it's not part of her job) to assist with identifying the ever-increasing heap of bones being pulled out of the site. And poor decisions in prior seasons sometimes come back to haunt our characters, months or even years later. Some bad decisions they get away with. It's ... almost like life.
I love this show.