Greg (laughs): You know what a "switch" is?
Grissom: Someone who's dominant as well as submissive. (Greg is thoroughly impressed. He turns to Catherine)
Greg: Oh, he's even got the lingo down. (Catherine nods her head. He imitates cracking a whip. Grissom doesn't crack a smile, Greg stops smiling and looks towards the floor)
Grissom: If Mona's DNA is in one of these masks, then she was the submissive on the night she died.
Greg: You're so dialed into this case, I'll bet you don't need me to tell you which mask had her DNA.
Grissom: Yes, I do, Greg. I also need to know which straw she used. (Greg turns around. Grissom looks at Catherine, she shrugs. Greg turns back around with two sharpie pens in his nose. One red and one blue. Grissom still doesn't crack a smile)
Catherine: Oh, nice. Mmm. Yeah, that's the idea, Greg. Two straws per mask.
Greg: You can't get any air through pens.
Catherine: And not much more through straws.
Grissom: And even less if someone's fingers are on the other end.
Greg: I found the victim's DNA on this mask and... these two straws. Red mark: Victim; blue mark ...
Grissom: Our killer. Now we just need a suspect.