Mills: Just because the fucker's got a library card doesn't make him Yoda.
Somerset: How much money you got?
Mills: I got fifty, fifty bucks.
Somerset: I propose a field trip; Come on, we'll make a list. At the top, we’ll put "Purgatory," "Canterbury Tales," anything relating to the Seven Deadly Sins. Ask yourself-
Mills: Hey, wait, wait.
Somerset: What would he study to do the things he's done? What are his interests now? Jack the Ripper for instance?
Mills: Where are we going?
Somerset: The library.
Man1: Coupons. Coupons. Free coupons. Discount, discount coupons.
Somerset: They must have had about fifty health violations during their last inspection.
Mills: Could you at least sit across from me? I don't want people thinkin’ we're dating.
Somerset: Give me your money.
Mills: I'm giving you this but if some stranger walks up they ought to know what the fuck we're doing. Fuck.
Man2: Hey, Somerset. How you doin’?
Man: I didn't figure this was gonna be a menage a trois.
Somerset: It's not a problem. Sit down.
Man: Only for you do I do this. It's a big risk. I figure we're just fair and square.
Somerset: It's a deal.
Man: All right. About an hour.
Mills: Yeah, help yourself. Well, that was money well spent?
Somerset: Yeah. All right, by telling you this, I'm trusting you more than I trust most people.
Mills: Well, good, because I'm about ready to punch you.
Somerset: It's probably nothing but even it is, it's no skin off our teeth. The guy in the pizza parlor is a friend from the Bureau.
Mills: Who? Stinky man?
Somerset: See, for years, the FBI has been into the library system, keeping records.
Mills: Mhm. Assessing fines.
Somerset: No. Monitoring reading habits. Look, come on, certain books are flagged. Books on, say, nuclear weapons or "Mein Kampf." Anyone who checks out a flagged book has his library records fed into the FBI’s computers from then on.
Mills: Wait, wait, wait. How is this legal?
Somerset: Legal, illegal, these terms don't apply. You can't use the information directly. It's just a useful guide. It might sound silly, but he can't get a library card without an ID and a current phone number. See?
Mills: So they run a list.
Somerset: Precisely. If you want to know who's reading "Purgatory" and "Paradise Lost" and "Helter Skelter," the FBI's computers will tell us.
1 field trip
指的是“实地考察旅行”：an excursion, an activity, usually with an intended purpose，比如去博物馆啊，森林啊，或是其他什么馆藏、建筑等等。
2. coupon 优惠卷
3. They must have had about fifty health violations during their last inspection.
Because Somerset thinks the café is dirty, he jokes that it is in trouble with the Health Dept. who serve health violations (违反卫生规定而被传讯) to dirty cafes.
4. sit across 对面而坐
Meaning Mills doesn’t like Somerset sitting alongside him so close, better that he sit opposite him in case people think they are gay.
5. ménage à trois.
Ménage à trois is the French term describing a relationship or domestic arrangement in which three people, often a married couple and another lover, share a sexual relationship, although the relationship might or might not involve all three persons having sexual relations with each other. The French phrase literally translates as "household of three".
6. fair and square
意思是“公平，公正，诚实，正大光明的”，比如：He won the race fair and square. 他正大光明地赢得了比赛。
7. no skin off one’s teeth
这个俚语也可以写作no skin off one's back / nose，意思是“of no interest or concern or involving no risk to one 不关某人的事”。比如：It’s no skin off my nose as to whether or not I get invited to the party. 他们邀不邀请我去聚会都不关我的事。