After bringing the Avengers a warning of impending doom, an amnesiac Hercules has been captured by Ares. Thus the current team of Avengers calls out to all their members, past and present. Traveling to the Black Knight's castle for aid, everyone who’s ever been an Avenger arrives, including even the Hulk who is convinced to join the fight.
The group enters the Black Knight's castle. In the basement, Dane summons the spirit of his ancestor, the original Black Knight, who reveals to them the chain of events that brought all of them together.
He explains that after the Knight relinquished his ebony blade (in Avengers #84), it had materialized in the realm of Olympus and became embedded in a tree where it was found and retrieved by Ares. Shortly afterward, Ares was joined by the Enchantress who arrived in Olympus and told him of the power that the sword wielded. Ares used it to snuff out the Promethean flame, turning all the Olympians (save himself and Hercules) into crystals.
Believing in an ancient prophecy that foretold of a war god with a sword crafted by a wizard who would one day rule all worlds, Ares gathered up a horde of mythical beings native to the Olympian realm as his private army in order to capture Hercules and expel him. When Hercules finally landed on Earth, the traumatic trip had caused his amnesia.
The original Black Knight’s spirit goes on to recap the events of the past few issues. With the story finished, the Avengers plan to travel to Olympus to fight Ares. They are joined by the Swordsman who has been watching the whole time. The Swordsman, a one-time Avenger in the past, offers his aid which the Avengers reluctantly accept.
The group splits in two, one group remaining on Earth to battle any Olympian invaders and the other to travel to Olympus to free Hercules and stop Ares.
A battle erupts in Olympus against the Avengers. Meanwhile, the other group fends off the first wave of invaders who have begun appearing in England. As both battles rage on, the Black Knight tackles Ares alone and the Hulk is attracted to the portal to Earth by the flute-playing satyrs gathered there.
The Avengers defeat Ares and the Black Knight reclaims his ebony blade. Fearing impending defeat, the Enchantress calls back the invading army back to Olympus through the portal to fight off the Avengers in Olympus. But their return disturbs the Hulk enough to goad him into attacking them.
In the aftermath, the Avengers gather at the portal. They leave Hercules to mete out punishment to Ares and the Enchantress while the rest return home. Hercules and Thor then use their combined might to close the portal.
With their mission accomplished, the remaining Avengers on Earth are questioned by the police about what was going on. Thor merely responds "Don't ask!"
