The scene takes place in Cydonia, on the isle of Crete soon after the end of the Trojan war.—
In the first act Ilia, daughter of Priam, bewails her unhappy fate, but won by the magnanimity of Idamantes, son of Idomeneus, King of Crete, who relieves the captive Trojans from their fetters, she begins to love him, much against her own will. Electra, daughter of Agamemnon, who also loves Idamantes perceives with fury his predilection for the captive princess and endeavours to regain his heart.
Arbaces, the High-Priest enters, to announce that Idomeneus has perished at sea in a tempest. All bewail this misfortune and hasten to the strand to pray to the gods for safety.
But Idomeneus is not dead. Poseidon, whose help he invoked in his direst need, has saved him, Idomeneus vowing to sacrifice to the God the first mortal whom he should encounter on landing.—Unfortunately it is his own son, who comes to the strand to mourn for his beloved father.—Idomeneus, having been absent during the siege of Troy for ten years, at first fails to recognize his son. But when the truth dawns on both, the son's joy is as great as the father's misery. Terrified the latter turns from the aggrieved and bewildered Idamantes. Meanwhile the King's escort has also safely landed and all thank Poseidon for their delivery.
In the second act Idomeneus takes counsel with Arbaces, and resolves to send his son away, in order to save him from the impending evil. The King speaks to Ilia, whose love for Idamantes he soon divines. This only adds to his poignant distress.—Electra, hearing that she is to accompany Idamantes to Argos is radiant, hoping that her former lover may then forget Ilia. They take a tender farewell from Idomeneus, but just when they are about to embark, a dreadful tempest arises, and a monster emerges from the waves, filling all present with awe and terror.
In the third act Idamantes seeks Ilia to bid her farewell. Not anticipating the reason of his father's grief, which he takes for hate, he is resolved to die for his country, by either vanquishing the dreadful monster, sent by Poseidon's wrath, or by perishing in the combat.
Ilia, unable to conceal her love for him any longer, bids him live, live for her. In his new-found happiness Idamantes forgets his grief, and when his father surprises the lovers, he implores him to calm his wrath, and rushes away, firmly resolved to destroy the monster.—
With terrible misgivings Idomeneus sees Arbaces approach, who announces that the people are in open rebellion against him. The King hastens to the temple, where he is received with remonstrances by the High-Priest, who shows him the horrid ravages, which Poseidon's wrath has achieved through the monster; he entreats him to name the victim for the sacrifice and to satisfy the wishes of the God. Rent by remorse and pain Idomeneus finally names his son.