press the x button. you and your crew will be invisible only for as long as the eye in the upper right by your "danger map" is closed. Once the eye opens, DONT MOVE AT ALL. once the eye disappears, press x again. in the time that you're invisible move your butt! But make sure you don't stop in front of a guard/master. also, if you get to certain parts, even if you're "caught" you don't have to go back too far. Good luck!