Calibos, the spoiled and rebellious son of the sea goddess Thetis, is betrothed to Princess Andromeda, daughter of Queen Cassiopeia of Joppa; but for committing several atrocities against Zeus, including destroying Zeus's sacred flying horses (except for Pegasus), Zeus transforms Calibos into a deformed monstrous satyr-like creature. In revenge, Thetis transports an adult Perseus from Seriphos to an abandoned amphitheater in Joppa, where he befriends a soldier, Thallo, and an elderly poet named Ammon and learns that Andromeda is under a curse and cannot marry unless her suitor, upon the threat of execution if he fails, successfully answers a riddle concocted by Calibos. Zeus sends Perseus a god-crafted helmet from Athena which makes its wearer invisible, a magical sword from Aphrodite, and a shield from Hera.