At th it's time of night you can't afford to get caught sneaking around the castle, so when you reach the library on the second floor, you will have to give several prefects on patrol the slip. Let me stress that you should also be weary of those magical books which fling themselves at you, causing you to lose your precious beans and some life. Before, if you get caught during stealthy operations, the consequences weren't bad, if there were any at all. However th it's time, if you are caught, up to 10 points will be deducted from Gryffindor. If you continue to blow your cover, the subtracted points will add up pretty quickly, so don't take th it's for granted!