Night in Hogwarts

Its Evening again and Night Duty Officer must switch on Lights in all Hogwarts as he do it every Evening, but Tonight is different.. Lights dont switch on and Hogwart`s sink in darkness. Duty Officer walk to the basement to see, what wrong and find Professor Severin Snape do something secretly (you are Duty Officer). Does he punish old Duty Officer about what he saw? What is it?