What is the theme behind the story the case for the defence by graham greene

In my opinion, there are various themes that you might
find in this story.  I will discuss what I think is the most important
theme.

I think that this story is about how far evil people
will go to accomplish their goals and how "civilized" society is helpless in the face of
such tactics.  Evil overcomes good.  You can see that in this story because the
civilized people are completely unable to do anything to the Adams twins.  They only
punish the twins by reverting to savagery themselves.

Even
after they do this, the author implies that the witnesses (who tried to act in a
civilized way) will be in mortal danger from the surviving twin.