Summary of Act IV
Prospero stops Ferdinand's punishment, and decides to finally give Miranda to him, since he has proven his love for her through his service. Prospero accepts the union, but issues them a warning; if Ferdinand takes Miranda's virginity before a ceremony can be performed, then their union will be cursed. Ferdinand swears to Prospero that they shall wait until the ceremony to consummate their marriage, and then Prospero calls upon Ariel to perform one of his last acts of magic. A betrothal masque is performed for the party by some of Prospero's magical spirits; Juno, Ceres, and Iris are the goddesses who are represented within the masque, and the play speaks about the bounties of a good marriage, and blesses the happy couple. This act of magic so captivates Prospero that he forgets Caliban's plot to kill him; for a moment, he almost loses control, but manages to pull himself out of his reverie and take action.
Caliban, Stephano, and Trinculo come looking for Prospero, and swipe a few garments of Prospero's on their way. Caliban still wants very much to kill Prospero, and carry out this plot; however, Trinculo and Stephano are very drunk, as usual, and prove completely incapable of anything but petty theft. Prospero catches themnot difficult, since they are making a huge amount of noise--and sends Ariel after them as they flee.