AKA covert ops, it is a plan in which you don't want your targets to know what it is that you're doing, because it usually involves something unpleasant for your targets. This means you have to conceal your presence and actions from your target and possibly bystanders by means of hiding in shadows, disabling surveilence equipment, etc. so that you don't hear the dreadful phrase Guards! Guards! shatter the stillness of the night. You might want to move silently as well.