Final answer:
The murderer tells Macbeth that Banquo is dead but Fleance has escaped, causing Macbeth to feel anxious about his insecure royal position.
Step-by-step explanation:
In the play Macbeth by William Shakespeare, the murderer reveals to Macbeth that Banquo has been killed but Fleance has escaped. This information causes Macbeth to react with anxiety rather than fury. He fears that the witches' prophecy regarding Banquo's descendants might still come true, which threatens his position as king. Macbeth muses about the imperfection of the murderous act, feeling unsettled that Fleance is alive and might still challenge his authority in the future.