The X-Men were at a relatively stable point in their lives at the beginning of the Dark Phoenix Saga (the book's creative team during this time was Chris Claremont and John Byrne). The team had finally reunited with Professor X and Phoenix, who had believed that the rest of the team had died months earlier in a battle with Magneto. With the team together again, Professox X felt it was a good time to go about adding new mutants to the school, and sent the team after a young teenage mutant in Chicago known as Kitty Pryde.
Unbeknownst to the X-Men, Phoenix had been manipulated by the evil mutant, Mastermind, during the time that the rest of the group had been missing. Mastermind felt that his control over Phoenix would allow him access to the Hellfire Club, a society club that secretly consisted mostly of evil mutants, particularly the "Kings" and "Queens" of the Club.
The X-Men encountered the White Queen of the Hellfire Club, Emma Frost, when they tried to recruit Kitty Pryde in "Uncanny X-Men" #129. Frost was also attempting to recruit Kitty for her group's purposes. Instead, Hellfire Club agents end up capturing the X-Men sent to Chicago – Storm, Wolverine and Colossus. Kitty Pryde, meanwhile, stows away with the bad guys to see if she can help her new friends. In the next issue, the other X-Men who had been in New York meeting another new mutant, the singing Dazzler, are notified by Kitty of the situation. They travel to Chicago to rescue their friends in "Uncanny X-Men" #131, where Phoenix and Emma Frost have a powerful telepathic battle. The X-Men rescue their friends, but Frost escapes.
In the next issue, the X-Men decide to take the fight to the Hellfire Club, especially when they learn that Warren Worthington, the former X-Men known as the Angel, actually has a membership in the Club!
Cyclops, Storm, Phoenix and Colossus attend a Hellfire Club function (while Nightcrawler and Wolverine sneak into the Club through the sewers). However, once there, Mastermind completes his work on Phoenix, transforming her into the Black Queen of the Hellfire Club, and she turns on her teammates. After a pitched battle, the X-Men are all captured, save for Wolverine who is seemingly killed. However, in perhaps the most famous Wolverine scene ever, we learn at the end of the issue that Wolverine is not actually dead. He has survived, and now he wants revenge.
The next issue sees Wolverine make his way to the prison where his teammates are being held, and he severely injures the Hellfire Club guards blocking his way in what was a pretty shocking fashion for the time the story was published. Meanwhile, Cyclops attempts to free Phoenix, but Mastermind begins a fight with Cyclops on the mental plane, and defeats the X-Man – almost killing him. This action causes the brainwashed Phoenix to begin to fight her programming.
In the final issue of the arc, Wolverine finally appears to save his friends, and Phoenix has turned back to the side of the heroes. She helps Cyclops escape, and the X-Men have their rematch with the Hellfire Club, which the X-Men win. However, Mastermind has pushed Phoenix too far – she snaps and becomes the Dark Phoenix.