Macduff suspects Malcolm and Donalbain of hiring their father's murderers because they fled from the scene immediately after their father's murder, which made it look like they were involved. Additionally, their sudden departure created doubt and suspicion among the other characters about their motives.
"Malcolm and Donalbain, the king's two sons, are stol'n away and fled, which puts upon them suspicion of the deed."
killing king duncan (:
Malcolm and Donalbain are suspected of murdering their father, King Duncan. After his murder, they flee Scotland for fear of their lives, leading many to believe they are responsible for the crime.
Macbeth Lady Macbeth Banquo Fleance Malcolm Donalbain Macduff Lady Macduff
Macduff believes that Malcolm and Donalbain, the sons of King Duncan, are responsible for killing their father.
Malcolm goes to England and Donalbain goes to Ireland (and that's the last we hear of him). They are taking a powder, believing rightly that they will be suspected of murdering their father. Ross, who loves to find out and deliver news, is going to Scone to check out Macbeth's coronation. Macduff, who doesn't like Macbeth much and is anyway somewhat antisocial, goes home to Fife. There he will make a point of refusing invitations to Macbeth's dinner parties.
At the beginning of the play, Macbeth didn't have any enemies. By the end he had lots, including Malcolm, Donalbain, Fleance and especially Macduff.
King Duncan had two sons: Malcolm and Donalbain. After fleeing Duncan's murder, Donalbain fled to Ireland, and Malcolm fled to England. Malcolm later led the attack on Dunsinane and took the throne after Macbeth was killed.
Malcolm and Donalbain fled for fear that they might be the next one's to be murdered.
Macduff assumed at first that Malcom and Donalbain hired the soldiers to kill their father and they fled to avoid any confrontations. However, it is evident that they fled because they suspected that they were the targets of a conspiracy.
There are six men who reign as king in Shakespeare's Macbeth: Duncan, Macbeth, Malcolm, Donalbain, Macbeth's son, and Macduff.
Macbeth, Lady Macbeth, Banquo, Fleance, Duncan, Malcolm, Donalbain, Macduff, Lady Macduff, their son, Lennox, Ross, Siward, Young Siward, the Porter, the Doctor, the Waiting Woman, and a number of messengers.