it then climbed to the top of the side of meat and gnawed its way through it around the hook until the mat dropped to the floor, at which point hundreds of waiting rats fell upon it.

여기서 at which point가 이해가 안 되서요.
point 가 빠지고, the floor, at which hundreds of waiting rats fell upon it.
이렇게 되면 어떤가요?