Lennox suspects everything that actually happened on the night Macbeth murdered King Duncan and on the next day when Malcolm and Donalbain fled for their lives. It is significant that it should be Lennox who conveys his strong suspicions to the Lord in very guarded words, because Lennox was characterized as a very young and naive man when he first appeared with Macduff. In Act II, scene 3, after describing the terrible storm he tells Macbeth:
My young remembrance cannot parallel
A fellow to it.
In the last scene of Act 3, which Shakespeare uses mainly to summarize what has happened, Lennox seems to have become mature, serious, and sophisticated in a short time as a result of living under a tyrant and having to treat Macbeth with formal courtesy while privately hating and loathing him for being a traitor and a villain. Lennox has learned innuendo and circumlocution. He conveys his meaning by saying just the opposite. For example:
And the right-valiant Banquo walk'd too late;
Whom, you may say, if't please you, Fleance kill'd,
For Fleance fled.
In such guarded and ambiguous language, the now older and wiser Lennox summarizes Macbeth's crimes. He murdered Duncan and killed the King's two grooms to keep them from talking. One of them may have actually seen Macbeth inside the King's bedchamber, according to what Macbeth tells his wife when he returns with the bloody daggers. Then when Malcolm and Donalbain decided to flee, Macbeth was able to blame Duncan's murder on them. Lennox is also sure that Macbeth had Banquo murdered. He is joking when he suggests that the crime might be blamed on Fleance because the boy fled for his life, just like Malcolm and Donalbain. This is very sophisticated dialogue for such young man. He has seen a lot of strange things in a very short time. He has even
It is significant that Shakespeare uses Lennox for all the exposition in this scene, because if this young man can understand everything Macbeth thought he was doing in extreme secrecy, then that must mean that everybody else must understand it just as well, although they are all prudent enough and frightened enough not to speak their minds to each other. Macduff is the only exception. He made it clear that he would not acknowledge Macbeth and then fled to England to join Malcolm.
Shakespeare often uses conversations between two characters to convey exposition to the audience. He handles this particular scene exceptionally well because he reveals the remarkable change that has taken place in Lennox during the period since the young man was talking to Macbeth outside Duncan's bedchamber while Macduff went in to wake the King and found him dead and covered with blood. The change in Lennox symbolizes the change that is taking place among all the nobility as well as all the peasantry of Scotland.
Lennox is also the appropriate character to relate the latest information about Macduff, since the two men were shown to have a close relationship when they first appeared to wake King Duncan.