Alonso the King of Naples' ship was struck by a tempest in a storm. The ship crashed against the rocks and everyone had to swim to shore.
The tempest was created by Prospero's magical slave. This was all part of Prospero's master plan to get revenge. Prospero and his daughter Miranda were banished to an island by his brother and Antonio and Alonso. This was a plot to overthrow Prospero
Ariel plays the flute to charm Ferdinand (a survivor of the ship that got separated) and he meets Miranda and they fall in love, which coincides with Prospero'splan.
Alonso, Sebastian, Antonio and Gonzala stop to sleep. Ariel plays the flute to force them to sleep, leaving only Antonio and Sebastian awake. They plot to kill Alonso and Gonzala whilst they are sleeping so they can rule Naples, but they wake up.
They take Ferdinand due to thinking he was dead, but they come across a feast that suddenly disappears and Prospero explains that he brought them all here to confront them. Alonso apologises for what he did and all is forgiven.
Ferdinand ad Miranda are married and happy, Ariel is set free and Prospero can become the Duke of Milan again and everyone returns to Italy.