The appearance vs. reality motif in the drama is expressed in these words of Lady Macbeth in Act I as she speaks to Macbeth about King Duncan's imminent arrival at Inverness, their castle. Because their ambition has been awakened by the prophecies of the witches, Macbeth and Lady Macbeth now entertain murderous thoughts about Duncan, thoughts of killing him so that Macbeth can assume the throne. They clearly do not want their thoughts known as they prepare to greet the King. Lady Macbeth cautions Macbeth about his appearance and instructs him as to his behavior:
Your face, my Thane, is as a book where men
May read strange matters. To beguile the time,
Look like the time; bear welcome in your eye,
Your hand, your tongue: look like th' innocent flower,
But be the serpent under 't.
Lady Macbeth is telling Macbeth that he must mask his real feelings about Duncan and appear to be the gracious, welcoming host. To deceive Duncan and his party, Macbeth must look like an "innocent flower," while he is really a serpent (poisonous snake) lying under it. In this way, false appearance will hide reality.