Blade

Classic Movie Line, Blade, Wesley Snipes is sitting in the car waiting for the police officer/traitor for the vampires to come out Karen's (being played by the beautiful actress N'Bushe Wright) apartment and lead him to his Boss/Handler. Karen ask Snipes "how do you know he will lead you to his handler", Snipes replies, "Once you understand the nature of a thing; you know what's it's capable of".

Translation: "Good or bad, we know what except from the people and things we are most familiar with."