Explain what was said or what happened in act 1 scene 4 of Macbeth?

Duncan demands to know whether the former Thane of Cawdor has been executed. His son Malcolm assures him that he has witnessed the former Thane’s becoming death. While Duncan muses about the fact that he placed "absolute trust" in the treacherous Thane, Macbeth enters. Duncan thanks Macbeth and Banquo for their loyalty and bravery. He consequently announces his decision to make his son Malcolm the heir to the throne of Scotland (something that would not have happened automatically, since his position was elected and not inherited). Duncan then states that he plans to visit Macbeth at his home in Inverness. Macbeth leaves to prepare his home for the royal visit, pondering the stumbling block of Malcolm that now hinders his ascension to the throne. The king follows with Banquo.