At the very end of Act II, scene III, Malcolm and his brother quickly confer about what they should do next. MacDuff and Macbeth have both agreed to go and put on their "manly readiness" to discuss the king's death, but the brothers both sense and fear "daggers in men's smiles," that is to say, neither of them feel that they can trust Macbeth or MacDuff at the time (153, 161).
Malcolm suggests that he will flee to England, and Donalbain to Ireland, where their "separated fortune shall keep [them] both the safer" (159-160). His suggestion reveals that he is unwilling to put on appearances for the Scottish lords and maintain the 'niceties' of courtly behavior. Malcolm and Donalbain both fear for their life, and are wise to do so. Staying a guest of Macbeth merely to follow proper social protocol would be a foolish mistake. Malcolm instructs his younger brother:
"Therefore to horse;(165)
And let us not be dainty of leave-taking,
But shift away" (165-167).
Both the brothers leave without a word to their host and hostess, a major social faux pas, but Malcolm has much more on his mind than social decorum at the moment.