Professor Xavier sends a plea for help to the Defenders to stop Magneto and his Brotherhood of Evil Mutants!
Dr. Strange shows Nighthawk, the newest Defender, around his Sanctum Sanctorum. Nighthawk similarly shows off his new costume. Before, he was just an acrobat in a cape. Now he has a jetpack hidden under his wings that allows him to fly.
However, Valkyrie explains that now she must go on her quest to find out more about Barbara Norriss, whose body she inhabits, as she originally planned to do three issues ago. Nighthawk is unhappy, since he just joined, and that leaves only him and Strange. However, he wants to help so he gets his assistant, Pennysworth, to buy a riding academy to house Val's flying horse, Aragorn.
However, as happened the last time she said she wanted to leave, Strange suddenly gets a psychic message. This time it's from Professor X. He needs help, and the X-men are unavailable. Once again deciding they need help, Strange decides they need the Hulk. However, instead of just forcing him to help, as he did with Namor two issues ago, Strange decides to actually ask, and Hulk agrees.
They all meet up with Professor X at Carlsbad Caverns in New Mexico. There they are attacked by a giant creature. It is beating them when Xavier makes it disappear--it is an illusion created by Mastermind. However, they are all knocked out by a burst of energy.
They wake up in a magnetic field created by Magneto. He explains that he is nurturing a "sleeper," who is growing in a cylinder, who will help him control the world. Magneto was last defeated by the Avengers, who put him in a force bubble in the center of the Earth. However, a passing comet changed the Earth's magnetic field enough that Magneto was able to escape. He found his way into the Carlsbad Caverns, where he discovered a long-ago civilization's technology. After learning the technology, he put together a team of evil mutants, including the Blob, Unus the Untouchable, Mastermind, and his previous creation, Lorelei.
After gloating, Magneto leaves. Xavier asks the Defenders to channel their thoughts through to him, and he uses all the electrical energy in their thoughts to break their magnetic prison. The mutants attack, but the Defenders defeat them. However, Magneto has had time to finish his work on the sleeper in the cylinder, and wakes him.