Alonso’s an important character to the play’s exploration of revenge and imprisonment because he suffers a very clear degradation of sanity as a result of guilt and grief. Because of Prospero’s revenge plot (which involves tricking Alonso into thinking his son is dead and a terrifying monologue by Ariel dressed as a harpy), Alonso becomes imprisoned by his sheer remorse for his plot against Prospero. He can only be truly free from his sins when he repents to Prospero and restores his dukedom. Only once this is done, Alonso is reintroduced to his son and all is well. He goes from being absolutely destroyed by the harpy’s speech, clear in his lament “O, it is monstrous, monstrous!” to liberated by the joy he finds in a reconciliation with Prospero’s family.
