In Act I Scene V, Lady Macbeth is seen reading a letter from her husband describing his encounter with the three witches and the prophecy that is fulfilled about him becoming the Thane of Cawdor. After reading, she begins to ponder how Macbeth can become King. She worries that his "nature" is "too full o' the milk of human kindness" to reach status of King by killing Duncan. She knows her husband is ambitious, but she also knows that he lacks the "illness" or wickedness to commit the crime. She ends by figuratively calling Macbeth to her so that she "pour [her] spirits" in his ear. In other words, she wants to convince Macbeth to kill Duncan. She knows she has the evil character to do it, and she wants to persuade and influence him with her wickedness so that he will take the crown by murderous force.