Atlantis is under the thrall of the warlord Attuma! Namor the Sub-Mariner, the rightful ruler of Atlantis, recruits Alpha Flight to help him take it back! And they'll have help doing it, from none other than Earth's Mightiest heroes, the Avengers!
Namor, the Sub-Mariner, sends Byrrah to recruit Alpha Flight to help rescue Marrina from the clutches of Attuma. Alpha Flight goes into the ocean to save their former teammate and find aid in the form of the Avengers. The two teams are forced to fight their way through an army of Atlanteans to retrieve Marrina.