Since the actual murder of King Duncan occurred offstage, and since Lady Macbeth went offstage to take the daggers back and to smear the faces of the grooms with blood, Shakespeare wanted to use the blood-covered hands of both Macbeth and his wife to demonstrate to the audience that a bloodly murder had been perpetrated. The actors would have smeared their hands with something red while offstage, possibly real blood from a slaughtered animal. Macbeth makes a great display of his hands. When he says that they pluck out his eyes, he probably holds his hands over his eyes and claws at his face, creating the impression that he is actually tearing out his eyes like Oedipus and then leaving red marks on his face when he uncovers his eyes. Then when he asks if all the great oceans can wash the blood clean from his hands, he probably pretends to put one hand in the ocean and stir it around and around. When Lady Macbeth tells him that her hands are of his color but she shames to wear a heart so white, she probably shows her hands so that the audience can see them and then wipes them across her breast leaving a big cross of blood on her white gown. Macbeth obviously feels horrified at what he has done, while his wife only seems concerned about bolstering her husband's resolution. The display of bloody hands and the dialogue that goes with it are a substitute for showing the actual murder. Shakespeare, for his own reasons, chose not to show the King being murdered in his bed. This choice was probably only made because it would have been too complicated to set up a bed-chamber with the King in bed and two unconscious grooms, when it was much easier to establish the fact of the murder and its horror the way he did.