Before the castle — the king arrives

Outside the castle of Inverness, late afternoon. Duncan arrives with Malcolm, Donalbain, Banquo, Lennox, Macduff, Ross, Angus, and the rest of the lords. He looks up at the walls and speaks one of the play's most painful lines. "This castle hath a pleasant seat. The air nimbly and sweetly recommends itself unto our gentle senses." He notes, in particular, the martlets — small swallows — that have built their nests in the eaves and the buttresses; "the air is delicate." Banquo, picking up the figure, agrees: where these birds breed and haunt, the air is blessed.

The whole exchange is twenty lines, and the dramatic irony is overwhelming. Duncan is admiring, in detail, the place where he is about to be murdered in his sleep. The audience has just heard, in the previous scene, Lady Macbeth begging the spirits to come in "the dunnest smoke of hell" so that her knife will not see its wound. The blessed air, the breeding birds, the pleasant seat — every image of natural goodness Duncan can find — Shakespeare puts into his mouth at the moment they are most cruelly false.

Lady Macbeth comes out of the castle. She greets Duncan in the perfectly tuned voice of a model hostess: "all our service in every point twice done and then done double were poor and single business, to contend against those honours wherewith your majesty loads our house." Duncan responds with answering grace, takes her hand, and asks to be led to her husband. She leads him in. The audience has watched, in this short transitional scene, the king walk into the trap with his eyes open and his manners impeccable. He is dead by the next time the lords gather, and the castle whose pleasant air he has just praised is the one in which his body will be found.