The deadly coils of Porcete and Caribea against Laocoön and his sons

Before the gates of Troy stands the enormous wooden horse left by the Greeks, who had sailed away pretending to abandon the war. It is the trick devised by Odysseus, hidden within its belly together with a band of Achaeans armed to the teeth: once the horse is brought within the walls, they will emerge under cover of night and slaughter their enemies. The Trojans, unaware, rejoice, but Laocoön, sensing the deception, utters the famous words «timeo Danaos, et dona ferentes», "I fear the Greeks, even when they bring gifts", which became proverbial, and hurls a spear against the horse's belly, which resounds ominously. Seeing his warning ignored, Laocoön, who has already sacrificed four sons to the cause of Troy, goes with the two survivors, Atiphates and Thymbraeus, too young to fight, to sacrifice a bull to Poseidon on the seashore so that he may avert the threat from the city. But suddenly Porcete and Caribea emerge from the waves, two enormous sea serpents sent by Pallas, who sides with the Greeks, and they throw themselves upon the two boys, crushing them in their coils: the same fate will befall their father, who rushes in vain to try to save them while everyone else flees.

The prodigy is seen by the Trojans as a clear sign that Laocoön's words were deceitful and that there is no danger in bringing the wooden horse into the city: the fall of Troy is sealed.