When the third appeared, he thrust at it with the knife, only to feel the blade[刀片] snap as the fish rolled. 
The stranger is an element of the group itself, not unlike the poor and sundry 'inner enemies'—an element whose membership within the group involves both being outside it and confronting it.
The power of organocatalysis is that it often provides surprisingly simple solutions to complex problems.
My fans are my motivation. Without them, I am nothing.