If there is any one thing that is great about The Wire, it's that it takes chances. It is not afraid to do what it needs to do, with plot and with characters, in order to tell the story they way it should be told.
McNulty and Freamon are still fashioning a serial killer who murders homeless people. This is a means to an end, with that end being the arrest and conviction of Marlo. Bunk still disapproves but is not ratting them out. How long will it be til they get caught? If they get caught? Who knows?
Mayor Carcetti wants to axe Commission Burrell, and succeeds but has to go through of crap to do it. And even in the end it didn't play out the way he wanted it to for political reasons. The media has already leaked the fact that Carcetti is grooming Daniels to be commissioner, a factor that indeed sped up Burrell "early retirement".
Omar is back and he's very pissed about the death of Butchie. He confronts Slim Charles about it. Slim said it wasn't Prop Joe's people. So in Omar's head that leaves one person: Marlo. It should get very interesting in the coming weeks.
Marlo has been going around Prop Joe's back to Vondas in order get a direct supply of drugs. In the end Prop Joe's nephew, Cheese, double crosses him and set's him up to get killed by Marlo and his men. When word of this gets back to Slim Charles, what will he do, align with Omar? 'Til Next week.