Macbeth at the beginning of the play is portrayed as an honest, loyal and brave subject. It is at the scene when he first encounters the three witches with Banquo that we see something click inside of him. They prophecize that Macbeth, Thane of Glamis is also Thane of Cawdor and will be king. The witches also say Banquo will be father to a line of kings. He is enticed with the prophecy that he will become king and this thought, whether it is a new one to him or not, really starts to tug away at his morals, honor, integrity. His wife, Lady Macbeth, though describes her husband as "too full o' the milk of human kindness." To be king is an alluring thought to Macbeth and killing the the rightful King Duncan to get to the crown does cross his mind, but Lady Macbeth has to manipulate and taunt her husband to convince him to do the deed.
When it's set in his head what's to be done, Macbeth on his way to Duncan's chamber, sees a bloody dagger floating in the air before him. Do his eyes deceive him? Is it real? He is unnerved but it does not take away his resolve to kill the king. His desire for the crown is stronger than knowing what is right. Macbeth kills Duncan and is wracked with regret, fear, guilt, sorrow. This time he hears voices saying he has murdered sleep. He comes into his own chamber to his wife, bloodied and wailing and falling apart. He cannot believe what he has done. He obviously is not truly evil at heart but this 'milk of human kindness' he is able to push away to achieve his evilly-motivated goal to be king. After this first murder the idea of killing to be able to get what he wants seems less horrific to Macbeth. He easily kills the king's servants the next day that he and Lady Macbeth have set up. This time he is a lot more able to cover up any sign of guilt, becoming a better liar, showing false face. Soon he is feeling more threatened by Banquo because Banquo knows about the prophecies of the witches, and also that one of the witches' predictions was that Banquo's sons would be kings but not his own. Macbeth doesn't think twice about killing Banquo, his friend, and Banquo's son Fleance. Macbeth is soon becoming paranoid having spies in the lords' houses and is happy with the news that Banquo is dead but upset with the news that Fleance escaped. That evening there is a banquet at Macbeth's castle and Macbeth sees Banquo's ghost and becomes unmanned and begins raving. Lady Macbeth has to send the guests away because Macbeth cannot be calmed down. He is behaving like a lunatic. Later Macbeth tells his wife that he is so far in, so "steeped in blood," that he cannot go back. The next day he goes to see the witches who give him new prophecies. They tell him to beware Macduff but also puff up his confidence saying no man born of woman can harm him and that he cannot be defeated until Birnam Wood comes to Dunsinane Hill. They also show M cbeth future kings who all look like Banquo and this enrages him. He says to himself that anyone who believes in the witches is damned. Macbeth himself relies on their prophecies, which we have to expect do not seem to be what they appear, so maybe Macbeth considers himself damned. He does not sense any more conscience pulling him back. He is afraid of Macduff, and although the other two prophecies give him a false security, he decides senselessly to kill Macduff's family, who have done nothing to him and are not a threat. Macbeth has completely turned himself to evil and accompanying madness here.