Hercules is startled when his mother Alcemene tells him she and king Jason, his friend the Argonaut, have been secretly in love since Amphitrion's death, and now plan a marriage. Under Corinthian law Jason may not continue to rule with a commoner wife, but can choose an heir- Iphicles is chosen and found in time. Of course Hera has a nasty surprise lurking: Perfidia, Echidia's largest brood, emerges from the sea and devours Jason, so Hercules jumps after him into the giant mouth...