While Hercules and his double, the Sovereign, were stuck in the Netherworld, Iolaus traveled back in time to protect young Alcmene. But he couldn't prevent Callisto from killing Hercules' mother. Callisto then found her own family and, through a series of instinctive actions, she killed her mother and father. As more events began to go wrong, Hercules sent Iolaus a telepathic message: Get the Chronus Stone from Xena's scepter to travel back in time without Ares' help. Using a makeshift lightning rod, Hercules joined Iolaus in the past and sent Callisto back into the vortex, setting the timeline right.

Hercules wanted to save the Norse god Balder, but Balder explained that his death was foretold in the Book of Fates and could not be changed. Sure enough, Hercules was tricked by Loki, the god of mischief, into accidently killing Balder. An enraged Thor tried to kill Hercules with his huge stone hammer, but Hercules beat Thor and took him to Valhalla. There, Odin -- the king of the Norse gods -- explained that two parts of an ancient prophesy had been fulfilled. If the third part took place, the final nightfall and end of all things would occur.

Hercules jumped through a vortex into the Netherworld. There he found his evil double, the Sovereign, as well as the cowardly double of his late sidekick, Iolaus. Disguising himself as the Sovereign, Hercules learned that Nebula, the parallel world's evil ruler, conspired with Ares to imprison the Gods of Olympus in the Labyrinth of Eternal Memory. Hercules and Iolaus battled a giant snake and entered the labyrinth. After defeating Ares and Nebula, Hercules freed the gods. The parallel Iolaus, wishing for a bright future in a new world, jumped through the vortex with Hercules.