What is the theme of the story, "The Catbird Seat"?

In this story about a meek, mild-mannered obsessive-compulsive man who sees his neat, ordered world that he loves falling apart due to a woman who is his polar opposite.  Mr. Martin fears that his job is about to be eliminated from the company where he works because Mrs. Barrows, a corporate re-organizer, doesn't see him as necessary.  In this way, there is a conflict between the two of them.  Martin has to figure a way to discredit Mrs. Barrows.  He hits upon the perfect plan - kill her.  When he can't find a murder weapon, he hits upon an even more diabolical plan - make her appear to be crazy.  Everyone knows Martin is a man who is addicted to his very conservative ways.  He never drinks or smokes.  He does all this and more in front of Mrs. Barrows, and then says he is going to blow up the boss, so the next day when she tells everyone about what she saw and heard, she is relieved of her position because she is believed to be crazy.  A theme shown by could be expressed: don't assume because someone looks like an easy mark, that he is.  Sometimes, it really is the quiet ones who are the most surprising.