In Act 2, Scene 3, after the discovery of Duncan's dead body, Malcolm and Donalbain agree to flee from Scotland because they fear for their own lives. Malcolm says, "I'll to England." Donalbain says, "To Ireland I. Our separated fortune / Shall keep us both the safer." Evidently both realize they will not be completely safe even if they leave the country. Whoever becomes king can send hired assassins to eliminate them.
