The internal rumblings of the police department come to a head in "St. Valentine's Day Massacre," placing Teresa in possibly her most difficult position yet, facing a vote of no confidence. She's confronted from all sides--from the mayor, the media, the public, and the officers--and each move she makes can have a large effect. If there's one thing that the episode shows us, it's that doing the job the right way pays off, as the criminal is caught and Teresa handles it like any other case.
There is a small subplot with Vonda and Isaac going up a vile attorney, who is also very perceptive, and the city is forced to pay. She mentions their relationship, so they could be running into more trouble soon.
Teresa and Jarek give Deion control of the gang, assuming he'll run it into the ground. Really? The writers better have a follow-up.