In Act Four, Scene 3, Macduff travels to England to get military support and convince Malcolm to return to Scotland with him. However, Malcolm is not sure that Macduff has pure intentions and does not fully trust him. Malcolm has every right to be cautious considering his father was murdered by someone who was trusted. Malcolm thinks that Macduff may be attempting to gain Macbeth's favor by getting him to return to Scotland. Despite the fact that Macduff insists that he is not a traitor and is loyal to Malcolm, Malcolm continues to test Macduff's loyalty by lying to him. Malcolm lies by saying that he has so many vices that the people of Scotland will think that Macbeth is as pure as snow compared to him. Malcolm also claims that he has insatiable lust and greed that will ruin his country. After hearing this, Macduff expresses his agony and reveals his honest emotions. Macduff's passionate outburst proves to Malcolm that he is a loyal, trustworthy man. Malcolm then agrees to follow and trust Macduff.