Now we're back to Alonso, Sebastian, Antonio, Gonzalo, and their attendant lords somewhere else on the island.
Gonzalo is weary, and Alonso has given up hope that his son might still be alive.
Antonio, hearing this news, utters an aside to Sebastian, reminding him of their plan. Antonio says they will murder the King tonight when everyone else sleeps.
Strange music then begins to play, and Prospero enters, invisible. Before the eyes of the King and shipwrecked lords, a magical banquet is laid by welcoming spirits who invite the King and company to eat. All wonder at the strange sight for a while, thinking they could now believe anything.
Sebastian is done with oohing and ahhing for a while, and suggests that since they are hungry, they should eat what the spirits have given them. Alonso refuses, and Gonzalo comforts him by saying there were lots of things they wouldn't have believed when they were young that turn out to be true—like girls don't actually have cooties and Santa isn't real.
Alonso decides to eat in spite of the risk, as "the best is past," meaning life can't get much worse than it is now. He invites everyone to the table.
Before they can dig in to their meal, Ariel appears in the shape of a harpy (a horrible monster with a woman's face and the body and claws of a vulture-like bird) and the food disappears. The harpy stuns the men, and declares that three men of sin are at the table. The harpy says Destiny has caused the sea to put them on this uninhabited land because they are men unfit to live.
The men draw their swords, and the harpy laughs at their foolishness, as their swords are no good against the natural elements she wields. The monster reminds them of the evil they did Prospero and the baby Miranda, and claims the sea paid them back for their crimes, taking Ferdinand and dooming the rest of them. If they repent their evil deeds, a better life might follow.
Ariel (as the harpy) then vanishes, and the spirits come once more to carry away the banquet table.
Prospero praises Ariel for his good work, which he has watched while invisible.
Gonzalo breaks the stunned silence when he asks what Alonso, Antonio, and Sebastian are looking so shocked about. (It seems Gonzalo didn't see the harpy.)
King Alonso admits that the sea and thunder spoke to him of his ill deeds against Prospero, and has claimed his son as punishment.
Sebastian and Antonio are unmoved. Instead of repenting, they agree to fight the ills that might befall them, one at a time.
As the three exit, Gonzalo notes that Alonso, Antonio, and Sebastian's treachery against Prospero is catching up to them. The kind councilor asks the rest of the group to follow the three traitors and stop them from whatever craziness they might attempt in their stunned, post-harpy encounter state.