Macbeth writes to lady Macbeth telling her of his encounter with the witches and how part of there prophesy had come true making him the Thane of Cawdor. In the letter Macbeth uses loving terms towards lady Macbeth such as 'my dearest partner of greatness' showing that he loved and respected her even in a letter, where he wouldn't be pressured by lady Macbeth into using these forms of affection. He tells her all of the witch's prophesies proving that he trusts her and is willing, if the prophesies come true, to share the wealth with her.
Macbeth starts to doubt whether he wants to kill king Duncan and almost talks himself out of it. Lady Macbeth quickly interferers and takes control of the situation and becoming the dominant role, this is important because in the times of the book women would normal (and nearly always) been told what to do by the man of the house hold and been made to cook and look after the children, so lady Macbeth taking charge of the situation shows her courage and somewhat Macbeth weakness not to stand up to his wife. She uses his manhood and pride against him saying he is not strong enough to kill king Duncan. After the conversation with lady Macbeth, Macbeth is persuaded to go ahead with the killing and lady Macbeth's plan on how it will happen.
So far there relationship has changed slightly with lady Macbeth having more control over Macbeth unlike at the start where there relationship was equal. She has the power over him to convince him to kill someone, even when he doesn't want to.
Macbeth is so shaken by the murder that he brings the bloody daggers with him from the scene, lady Macbeth quickly comes up with a plan to frame the guards and this time gets involved herself planting the knives on the guards. She still has control of the situation but has to step in herself because Macbeth refuses to go back and she again in...