Hercules is captured by Ares, prompting the Avengers to call out for aid from all their members, past and present. Traveling to the Black Knight's castle for aid, all the members arrive, including the Hulk who is convinced to join their fight. The group enter the Knights castle where in the basement he summons the spirit of his ancestor, the original Black Knight, who reveals to them the chain of events that brought all of them togeather:
He explains that after the Knight disposed of his black blade (back in Avengers #84) it had materialized and embedded in a tree in the realm of Olympus only to be found and retrieved by Ares. Shortly he was joined by Enchantress who arrived in Olympus, who tells Ares of the power the sword wields. Ares then used it to snuff out the Promethean flame turning all the Olympians, save himself and Hercules into crystal. Believing in an ancient prophecy that foretells of a war-god with a sword crafted by a wizard would one day rule all the world, Ares gathers up an army of other races found in Olympus as his private army that captured Hercules and tossed him from the realm. When Hercules finally landed on Earth the trip caused him amnesia. The spirit of the original Black Knight then goes on to recap the events of the past few issues. With his story finished, the Avengers vow to travel to Olympus to fight Ares, and are soon joined by the Swordsman who had been watching the whole time. The Swordsman, having been 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. As a battle rages on in Olympus against the Avengers, Hercules, Enchantress and Ares, the other group stops the first wave of invaders who have appeared in England. As the battle rages, the Black Knight tackles Ares alone and the Hulk is attracted to the portal to Earth by the pan flute playing satyrs that have gathered there.
Meanwhile, the Avengers manage to defeat Ares, and the Black Knight reclaims his black blade. Fearing impending defeat, the Enchantress goes to the portal and calls back the invading army back to Olympus to fight off the Avengers, however their return disturbs the Hulk enough to goad him into attacking them. The Avengers eventually gather at the portal where they leave Hercules to deal with the punishment of Ares and Enchantress while the rest return home to Earth. 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 gathered as to what was going on, in which Thor responds "... don't ask!"
NOTE: Jon Costa is a pseudonym for John Costanza.