Spoiler
I won't actually spoil the identity of the murderer here. I'll just say that I found it to be a fun reveal. The episode *does* come with a brief team-up between Nick Fury and Loki, however, which is pretty rad. With the original Avengers dead -- save Captain America, who still hasn't been unfrozen yet -- Loki also does wind up conquering the planet, and we get a glimpse of who's going to be rallied to stop him. But it's the murder mystery plot that's the real meat.
I didn't notice if they did this in the first two episodes, but there was a neat touch in this one where Uatu kept showing up on the skyline in the background of scenes (presumably invisible to the characters, but visible to us).