X-Men emergency indeed, Charles... the dream is over.
The story begins with the aftermath of the Assault on Weapon Plus story; unfortunately Chris Bachalo has left art chores, but Phil Jimenez delivers some great work to go with Grant Morrison's excellent story. A few of the X-Men are scattered with Cyclops and Fantomex in a shuttle crash over the ocean and Wolverine alone in a space station fighting Ultimaton. I actually can't recall much of the story beforehand, with it being years since I read it, so how we got to this exact situation isn't coming to me. Instantly beginning with some of the team in trouble, naturally the issue kicks off with a splash page of Professor X exclaiming "X-MEN EMERGENCY!".
Beast and Emma are dispatched to go and collect Cyclops and Fantomex while Jean heads off in an X-Plane to find Logan. Elsewhere at the Xavier School, Xorn is teaching his Special Class as he appears to induct Dust into the class, we only see the tail-end of the scene with Xorn asking Dust if she wants to join them. The way the scene is presented, a whole scene dedicated to what is basically one line, is decompression at it's finest. The fact it's drawn out sets the tone, it's meant to seem somewhat sinister but at the same time not clue the reader into the true nature of what we've just caught the end of. Not pointless or lazy decompression, it's appropriate.
The next scene sees Dust paying a visit to Professor X as Xavier shows her Cerebro and tries to bond and accommodate her. Picking up on her thoughts, Xavier learns of something concerning Xorn's apparent offer and believes she must be mistaken just as Xorn himself interferes and manipulates events so Dust destroys Cerebro, meaning the Professor can't contact his X-Men. And speaking of the X-Men, things aren't going great for them as Beast and Emma are shot out off the sky and Jean finds Wolverine only for them to realize too late what's really going on.
The highlight of the issue is the final scene... one of the greatest X-Men scenes ever written filled with more tension than one would think possible. It beings fairly ordinary with Professor X talking to Xorn in the latter's classroom about the nature of Dust's outburst. As the conversation goes on, Xorn slowly begins to display a harsher and more righteous tone which is completely out-of-character for Xorn. Professor X picks up on this and amidst the tense awkward silences he looks over at the wall and notices that Xorn has a map of the world on the wall hanging upside down. "Xorn... why is that map upside down?", he asks... already fearing the answer. Xorn responds, not with words, but with revelatory actions as he commands the doors to the classroom suddenly slammed shut and the locking mechanism is activated... magnetically... we know already... it is Magneto.
Magneto has been making a mockery of Xavier's dream for the last few months, operating under his nose and twisting his own pupils into his way of thinking. Having crippled Xavier's ability to contact his X-Men by having Dust demolish Cerebro, Magneto now LITERALLY cripples Xavier by revealing that for the past few months, rather than Xavier being healded by "Xorn", in actual fact, he had been holding Xavier up magnetically using Nano-Sentinels glued to his spine. Charles lies on the floor, crippled and helpless as Xorn's Class of students watch over him laughing and Magneto proclaims "the dream is over".
The immediate thing that warrants discussion is the Magneto reveal. Superbly handled with some perfectly tense dialogue, the reveal itself does raise a few interesting nuances and unanswered questions from the prior issues, but at the end of the day, Xorn being Magneto makes for one of the greatest X-Men stories ever told and some of the best Magneto character work ever.
There is a few criticisms one could direct at the issue, for the most part this is mostly and very obviously set-up - but it's entertaining set-up. The Xavier/Xorn scenes are ripe with so much subtext and undercurrent tension, you could have a cardiac arrest trying to cope between turning the pages. There's subtlety and a perfect play-off between Xavier and Xorn, but the factor that makes it stand-out is the nature of the reveal. The inherent tension flows so well into Xavier questioning the map and then the chills that run down your spine when the door's are instantly slammed shut and their locks turned through Magneto's will of magnetism. While the scope of two men conversing might not be epic in scope, the sequence is indisputably epic.
This is, without a doubt, Grant Morrison's crowning glory when it comes to X-Men. So naturally Marvel retconned every element of the story within a few months of Morrison leaving the book. Whereas Morrison's early work on X-Men was at times fraught with complexities or certain pretension that, while suitably apt to his stories, made them hard to swallow; what you have here, in this issue, is the opening chapter to the definitive Magneto story of the new age and one of the best X-Men stories ever told.