Might as well ask.

Not sure if it is the best idea, but not wanting to simply start killing people for doing their job, you decide the best option at this point is to ask where he is. Slipping out of the shadows a bit early so as not to startle the guards, and give you enough room to make an escape. "Hello, might I ask where the captain of the guard is? It is urgent that I speak with him."

The two guards look you over for a second, sizing you up, and obviously running your face over in their minds to try to remember something, when the one on the right draws his sword and shouts, "It is her, the assassin." Then trying to stare you down, he adds, "Drop your weapons and we will bring you in alive, if you try to fight, we will cut you down where you stand."

The second draws a crossbow, obviously not quite as positive of the outcome as his companion and simply adds, "Yeah."

Looking the two over you are pretty sure they aren't really much of a threat, although if you try to run the one with the crossbow might get lucky. With that in mind, do you really want to cut these two down?