You were looking for a special rock at a very high mountain, you were dangerously close to the edge, so you had to watch your step otherwise, you'll fall to your death. You were walking and searching for the stone, until you tripped and you fell off the edge. But you were quick enough to grab onto the edge of the cliff. You tried pulling yourself up, but that didn't work. Suddenly you felt a strong arm holding you

"Hold on tight!"

You glanced up and saw Snape. He saved you.