[She certainly hasn't survived this long in her line of work without almost having a sixth sense for when she was being watched. And she likes to think herself a rather good observationalist. So it's not hard to discover she's being sized up by another man in the library. And since she's not doing anything suspicious or fascinating, she can only assume it has something to do with her actual person.]

You know. [She starts casually, as she reaches up to grab a random book off the shelf just to turn it over in her hand] Usually at this point it's polite to introduce yourself, or it's necessary for me to pull out my can of mace.

[And then she puts the book right back.] Which shall it be?