Alonso is the King of Naples. An enemy of Prospero’s, he accepted Antonio’s proposition to help the latter usurp Prospero’s throne in return for Antonio’s swearing Milan’s fealty to Naples.
On his way back from the wedding of his daughter in Tunis, a storm casts him on a magic island, where he searches for his son Ferdinand, whom he barely dares hope may have survived the wreck. Ariel’s imprecations and condemnations at the vanishing feast wake remorse in him, and believing that Ferdinand has drowned, he runs off to do the same to himself. Trapped inside his mind, he wakens to find Prospero before him, and immediately returns the freedom of his Dukedom to him and begs for his pardon. He is reconciled with him, particularly when he discovers that his son is in fact alive, and he is more than happy to acquiesce to Ferdinand marrying Prospero’s daughter.