This cross-over featured three ongoing x-titles, X-Men, X-Factor, and the New Mutants.
Storm was depowered, she was also the Leader of the X-Men at this time. She was on a mission to find Forge a mutant inventor whom she hope could find a way to restore her former power.
This led the rest of the X-Men on a journey after her, the ended up crossing paths with Freedom Force, in Dallas,Texas. The Freedom Force was led by Mystique, and were a government supported team of ex-villains. Mystique and the Freedom Force were under strict orders to sub-due the X-Men for they had failed to comply with the rules of the Mutant Registration Act.
The two groups engage in a superpowered battle. In the midst of the battle the mutant known as Destiny catches a small glimpse of the near future. The vision show that everyone inside of a particular Skyscraper in Dallas will soon be dead.
Then when the weather changes to snowy in the middle of July in Dallas, as well as prehistoric creatures and other monsters begin to randomly appear, both teams realize that something of grave importance is going on. They put aside there differences for the time being and co-operate as one team to try and restore the balance.
Elsewhere Storm and Forge are in a new world where time moves at an accelerated rate. while only mere minutes pass in real time, Storm and Forge spend a year in this altered time. allowing Forge the time he needs to build a device that restores Storms powers. Forge and Storm combine their Magic and Lighting respectively to open a portal back to the real world and to Dallas.
Back in the city with the X-Men, the X-Team learns of something Forge did in the Vietnam War that created a being known as the Adversary whom is behind the madness and utter chaos surronding them.
Storm, Wolverine, Colossus, Rogue, Longshot, Dazzler, Psylocke, Havok, and Madelyne Pryor all end up having to sacrifice their lives just as destiny had forseen. The sacrificed themselves using Forge's Magic to bannish Adversary. Seeing that that the X-Men gave their lives to save humanity the goddess Roma granted them all their lives back as well as the ability to be invisible to anymeans of detection other than plain sight. She also gave them the Siege Perilous which give the X-men the ability to reset time.
Cyclops, Marvel Girl, Beast, Iceman and Caliban are transported aboard the evil mutant Apocalypse's where they are then offered the once in a lifetime chance of being on of Apocalypse's team to aid in his war against the humans. The X-Factor team refuses Apocalypse's offfer and is the pitted in battle against his four hoursemen, Death is revealed to bet the long thought deceased Angel, now re-born as Archangel. Archangel quickly and easily defeats the entire team, and restrains them all except for Caliban, who had now offered his services to Apocalypse in return for stronger powers. Caliban also begins to refer to himself as Archangel.
Apocalypse then turns his sights on New York City, and begins his attack. The young team known as Power Pack shows up and helps in defending the city, minimizing damage and casualties. This allows Iceman to form a plan to defeat Apocalypse. Iceman then attacks Apocalypse only to have his most powerful attacks easily repelled. Although Apocalypse fends off Iceman with ease, his airship is badly damaged, and his horsemen defeated. He withdraws before suffering further losses.
Cannonball, Cypher, Magik, Mirage, Sunspot, Warlock and Wolfsbane, all go to visit the island of their good friend Bird-Brain. While their the team learns that Bird-Brain's creator the Anti-Mator is creating new life and doing cruel experiments on them. During their Rescue attempt the team is interrupted by the Right who shoot and kill the language mastering mutant Cypher when he dodges in front of Wolfsbane saving her.eventually Bird-Brain and Magik defeat the Right and the Anti-Mator, by using Magik's abilities to transport the villains to Limbo. Magneto then blames the humans for Cypher's death, gives up on the X-Men's teachings.