Alcmene comes looking for Hercules and Iolaus to tell him she is getting married to Jason. Hercules is shocked by the news. The three travel onto Corinth to meet with Jason. In Corinth, Jason's adviser tells him that if he marries a commoner he cannot continue to reign as king. Hercules voices his concerns about the marriage to Jason, but Jason tells him they can talk about it later. In the castle, Jason's adviser is visited by the Blue Priest, who has been brought back to life by Hera. He plans to have Hercules killed at Alcmene's wedding.
While looking for fabric to make her wedding dress, a woman named Sera approaches Alcmene and says she has heard she and Jason cannot marry at the castle. She suggests they use her uncle's gardens and Alcmene says she will tell Jason. Elsewhere, in Corinth, Hercules and Iolaus run into Phoebe and some of the other Argonauts and Hercules discovers that Jason has to give up his crown to marry Alcmene. Jason confirms that it is true, and Hercules apologizes for being upset about wedding. Jason tells Hercules he wants him to take his place as king of Corinth. Hercules says he is honored but declines the offer. The Blue Priest arranges some mercenaries to kill Hercules at Alcmene's wedding. Jason sends Iolaus off to get someone else who can take his place as king.
Meanwhile, Iolaus meets Dirce, and invites her to the wedding and he takes her with him to find the mystery guest. Jason and Alcmene go to look at the gardens where they agree to have the wedding. While heading back to Corinth, Hercules, Jason and Alcmene are ambushed by the mercenaries. Hercules and Jason fight them, but when the finish they realize that Alcmene is missing.
They find her fighting on of the mercenaries, whom she knocks down a hill. At the gardens, the Blue Priest stands atop a stone monument chanting, in the sea below a huge monster stirs. Later, at the wedding festivities, Hercules is looking for Amphion, who will be performing the ceremony, and he meets Deric who says he recognizes Sera, but then puts it down to his memory playing tricks. Jason and Alcmene arrive and wedding guests go to the gardens.
At the gardens, the Blue Priest prepares everything for Hercules's death. As Jason and Alcmene prepare to marry, Hercules wonders where Iolaus is. Jason proclaims that Hercules's brother, Iphicles is to be the new king of Corinth. Jason passes the crown over to Iphicles and pronounces the new king of Corinth.
Deric recognizes Sera as a spy for Hera and tells Hercules. As Amphion prepares to marry Jason and Alcmene, the sea monster appears and the guests flee. The waiters at the wedding are revealed to be mercenaries and they attack the guests. Iphicles, Jason, Iolaus and Hercules fight them. Jason is caught by the sea monster and as it swallows Jason, Hercules jumps into its open mouth to save Jason.
Inside the monster, Hercules tells Jason, "I've been inside one of these before." Back at the wedding, Alcmene hits Sera, calling her a "treacherous little witch." Inside the monster, Hercules and Jason make their way through the creature. Iolaus fight with the Blue Priest, who calls for Hera's help and jumps into the sea. While Hercules and Jason try to get out of the creature's stomach, it is being attacked by another sea monster; they make their way to the creature's mouth and escape to the surface.
Later with everyone safe and the mercenaries taken care of, Amphion marries Jason and Alcmene.