Renée Ballard works the overnight shift at LA's Hollywood station aka The Late Show. Cops on this shift don't get to follow their cases - they respond to calls, get information and start the paperwork for the daytime crews to take over. This is why it's considered a punishment for cops that have screwed up in some way. It's rather unfulfilling, and Ballard struggles against this - she's a good cop, and wants to finish a case. She finds a way to keep working on all three of the cases she gets a call out on.