Don Flack: Got any bad habits, Arnold? For instance, I crack my knuckles. It used to drive my mom nuts (his knuckles crack) Some people pick their nose, chew with their mouths open, use a pen knife to clean their fingernails in public.
Arnold Vonley: So what? That's a crime now?
Don Flack: No, Arnold, that's not a crime. It's disgusting, but it's not a crime. Unless, of course, you use that same pen knife to mug someone.

Don Flack: Guess who walks out?

Don Flack: Hey Mac. Bet you a cup of coffee this is the most interesting crime scene you'll go to all week.
Mac Taylor: You sound confident, obviously you know something I don't.
Don Flack: [To Sheldon] You wanna tell him?
Sheldon Hawkes: No, please.
Don Flack: Alright. [To Mac] You had to guess, how old do you say our victim is?
Mac Taylor: Late seventies, early eighties maybe.
[Sheldon and Flack smile and nod as if it was a good guess, Mac looks at them confused]

Don Flack: How did she get here without getting caught?
Mac Taylor: Buildings on either side are abandoned. No one has been up here for years.
Don Flack: What the hell was she doing in here?
Mac Taylor: Looks like Tessa was living here.
Don Flack: Whoa...[They find a wall plastered with Newspaper clippings, polaroids of people, masks...] I don't think the elevator goes to the top floor, if you know what I mean.
Jo Danville: Its amazing.
Mac Taylor: Somewhere in here is the answer to what Tessa was trying to tell me.

Don Flack: How often you keep the place open after 4:00 a.m.? [Witness hesitant to answer] Mr. Lannigan, I thought this might go without saying but I'm more interested in the body lying in front of your bar than what was going on inside.

Don Flack: How the heck did he survive all that time?
Mac Taylor: If you're asking the scientist, I'd say his particular body chemistry metabolized the poison slow enough to keep him breathing. Drinking condensation kept him alive. But if you want my personal opinion, I'd say science didn't have anything to do with it.
Don Flack: It's too bad they all can't have a happy ending.

Don Flack: I can't imagine what that withdrawal thing feels like.
Mike Black: Kind of like a cop who can't get a donut.

Don Flack: I'm good. I'm pissed. Hazel Ortega got shot in my custody.
Mac Taylor: And they would have killed her if you didn't get off some shots. There was nothing you could do. This was an organized hit and she was the target.

Don Flack: John Brennan calls the station house once a month. And anyone who answers the phone gets a story about how his wife was murdered, and the man responsible is still out there. And it breaks your heart. Because you don't have any answers for him. But what can you do? Tell me, on those Mondays, when you hung up the phone, what did you do? [Stella shakes her head a little] You can't do much. Because you are chasing bad guys, who are out there right now, and the evidence on those old cases gets cold, and the witnesses don't remember half of what they used to, and-
Stella Bonasera: You're right. But I just can't stop thinking that I should've done more to help her find her brother.
Don Flack: You took her calls every Monday. That's a lot.

Don Flack: Last time I checked, the murder weapon we confiscated didn't have cute little legs, walking around from toolbox to toolbox.

Don Flack: Maybe it's me, but I don't get it. You get 80 laps jammed into that tiny car; 10 second pit stops... Where do you go to the bathroom?
Mac Taylor: You don't wanna know.

Don Flack: Mrs. Anderson... we're going to find the guy who murdered your son.
Mrs. Anderson: That's not going to bring him back, is it? I'm sorry.
Don Flack: It's going to take time.
Mrs. Anderson: I don't know the right way to act around people, what to say to them.
Don Flack: No right way to act. Children aren't supposed to die.
Mrs. Anderson: I would like to see him, Detective.
Don Flack: All due respect, I don't think that's a good idea. That's not how you want to remember him.
Mrs. Anderson: Then, how do I say good-bye?
Don Flack: You don't. Not where it counts.

Don Flack: No way Arnold did it. He's strictly small time. Muggings. Petty theft.
Sheldon Hawkes: So he robs our John Doe and leaves behind a bag worth five mil.
Don Flack: Yep, I guarantee you he will regret that decision for a very long time.

Don Flack: Put it this way: if a dishwasher and a porta-potty ever mixed it up, this thing would be their offspring.

Don Flack: Recognize our robbery vic?
Mac Taylor: Roland Carson, defense attorney.
Don Flack: I prefer scumbag lawyer but, yeah, that's him. Body belongs to Melvin La Grange. He was a drug dealer whose hobbies include murder and extortion.
Mac Taylor: Let me guess, scumbag's client?