In this scene  Macduff & Malcolm have been discussing issues about Macbeth about him not being a Nobel king. he has murrdered the old king Duncan and also murrdered Banquo. Macbeth’s on friend stabbed him right in the back. Macduff mentions behind his back (Macbeth is a treacherous king) Malcolm’s suspicions dismary Macduff.Malcome tells him that he has english troops to support his cause,that his own vices are far worse than Macbeth