Party Girl: Thank you. Catherine: (voiceover) Being a detective is about drawing lines: the lines between us and them, good guys and bad guys, perp and victim. Party Girl: Hey, uh, you must've drunk-texted me. There's no party here. There's nobody here. Um, call me back before my phone dies, okay? Catherine: (voiceover) Then there are the lines we draw to protect ourselves: rules, protocol. It's about not crossing those lines because when you do...bad things can happen.