In William Shakespeare's Macbeth (I,v), Lady Macbeth is seen reading a letter she has received from her husband (Macbeth). In the letter, Lady Macbeth learns that Macbeth encountered witches who prophesied his climb to king.
Lady Macbeth ponders Macbeth's ability to "catch the nearest way" to the throne. She believes him to be far too kind. She compares Macbeth to an infant (he is "too full o'the milk"). Later, after a messenger brings word that Duncan is on his way, Lady Macbeth's true nature emerges. She asks to be "unsexed" and filled with "direst cruelty." She renounces peace, remorse, and God ("nor heaven peep").
Readers learn that Lady Macbeth is a woman who desires power more than anything. Her husband does not mean much to her (given her comparison of him to a child). She knows that she can only count on herself to do what needs to be done. Essentially, Lady Macbeth proves herself to be ambitious, ruthless, and manipulative.