In order to placate the angry gods, who have allowed Thessaly to be overrun with barbarian invaders and beset with natural disasters, King Jason takes his Argonauts on a search for the fabled Golden Fleece. Meanwhile, back at home, his scheming regent is plotting to get his hands on the kingdom--and the queen.

The evil King Zagro has designs on the beautiful Princess Sira. He wants to marry her so he can take over her kingdom and add it to his own. When Sira is kidnapped, Ursus leaves his farm to rescue her and to eventually lead a revolt against King Zagro.

An American agent disappears after a scuba diving reconnaissance mission in Corsica. The Secret Service sends agent code name OSS 117 to investigate.