"Infirm of purpose! Give me the daggers. The sleeping and the dead are but as pictures".
Macbeth sees a floating dagger in front of him. He wonders if this is a hallucination or if the witches made the dagger appear in front of him. The dagger starts dripping blood, and points toward Duncan's room. This makes him pull out his own dagger. He takes this as a sign, and when he hears a bell ring, it convinces him he should go kill Duncan immediately.
Lady Macbeth hears an owl scream. She wonders why Macbeth is taking so long. Macbeth enters with his bloody hands holding two daggers. Lady Macbeth is telling him it was incriminating to bring the daggers to their room. She's going to take them back because Macbeth is too scared to do it himself.
Lady Macbeth comes back from planting the daggers on the guards. Lady Macbeth tells Macbeth to not think about what he just did because it will drive them both crazy. They hear a knocking on the door, and quickly change into their nightgowns. They start to act naturally so no one would suspect them because if someone discovered them, they would be ruined.