Macbeth expresses how he fears Banquo because he is a noble man who is willing to take risks. Macbeth remembers that the three witches prophesied that Banquo's son would become king and his descendants would inherit the title for generations. Therefore, Macbeth orders assassins to kill Banquo and his son, Fleance, in hopes of thwarting destiny. However, in Act 3, Scene 4, Macbeth receives news that Banquo was murdered, but his son escaped. Macbeth is initially pleased that Banquo is dead but becomes afraid again after hearing that Fleance is alive. Macbeth says that he went from being "Whole as the marble, founded as the rock" to being "...cabined, cribbed, confined, bound in to saucy doubts and fears" (Shakespeare 3.4.23-26). Macbeth is no longer confident because his plan did not work to perfection. He knows that eventually Fleance will return to become king and compares him to a young snake. Although Fleance is not dangerous at the moment, in time he will be as dangerous as a poisonous viper.