Malcolm, from William Shakespeare's tragic play Macbeth, has only one motive behind his behavior as seen throughout the play. First and foremost, Malcolm's behaviors are those which insure that he will be able to take the crown back from Macbeth and restore it to the family line, his, which truly deserves it.
Malcolm's escape to England was necessary to insure his safety. If Malcolm would not have left for England, the chances are that Macbeth would have tried to, and succeeded in, killing him.
Once in England, Malcolm was able to gain the support of the king. With the support of the King of England, Malcolm was able to return to Scotland and declare war upon Macbeth.
Upon his return to Scotland, Malcolm was able to defeat Macbeth and reclaim the crown--and avenge his father's death.