Grieving over the loss of Iolaus, Hercules vows to persuade the Sumerian gods to bring him back from their underworld. Reluctantly accompanied by Nebula, he sets off on his quest, but many things stand in their way.
Hope frees Callisto from her prison and sends her back through time to prevent Hercules from being born. Iolaus convinces Ares to send him back to stop her.
Iolaus returns from beyond the grave to warn Hercules that the end of the world is at hand. The Archangel Michael is bringing about the apocalypse by releasing the Four Horsemen onto the land.
Hercules is enjoying life in Eire, where he is getting close to Morrigan. But visions of Nebula in danger lead him and Morrigan back to Sumeria, where they find Nebula on the brink of insanity after visions of the dead Iolaus.
Darphus, revived by Ares, is pillaging everything in sight to feed a monster called Graegus. Hercules and a redeemed Xena are determined to stop him. Iolaus joins Hercules but has trouble believing she is really reformed.
Hercules has a nasty surprise for his birthday when Xena's mortal foe Callisto makes a deal with Hera to escape the afterlife and drug Herc's family, in a plot to kill the half-god in return for her freedom.
