As the X-Men return to Westchester, an impatient Havok and Lorna Dane, dressed in their costumes, are waiting for them on the doorstep and order them to change to their fighting garbs. They have no time! The senior X-Men don’t take their attitude too well, and a jealous Bobby Drake asks Lorna why she didn’t even say ‘hello’ first. Jean and Scott try to play peacemakers.
Havok tells Lorna to convince them. She reaches out and magnetically uses a lantern post to usher the others inside. Beast angrily bends the post’s metal, refusing to be prodded like some animal. Bobby attacks with an iceblast, but Havok melts it with his cosmic power. He tells them he has a good reason and orders them to stop acting like kids and do as they say! They haven’t a second to waste! He tells Scott to act like a leader. Scott interrupts Alex has made his point. They’ll assemble in the computer chamber.
The senior X-Men change in their rooms first. Marvel Girl observes that Lorna and Alex seem to mesh, which won’t do Iceman’s morale any good.
Beast worries about their exhaustion due to their constant travails.
Scott finds himself resenting his brother’s leadership ability and Iceman tries to convince himself he doesn’t care about Lorna giving him the cold shoulder.
Angel is pensive reflecting on his mortality. He is the last to enter the computer chamber, earning him a reprimand by Havok. Pointing to the alien-looking creature on the screen, Angel asks what this nightmare is. According to their little tin Hitler, it’s real, Iceman remarks.
Real and powerful, Havok agrees. They saw a prime specimen of the Z’nox, a star-spawned race from the Andromeda galaxy, utterly dedicated to plunder and enslavement. Far back in Z’nox history, evolution soured. It produced a race absolutely lacking in compassion. Their only art is war, their only joy death. About a millennium ago, Z’nox scientists devised the ultimate weapon. They created a gravity transformer drive strong enough to transport their entire planet anywhere in the cosmos.
Iceman doesn’t buy this, mocking he’s seen scarier stories on Star Trek. And even if it’s true, so what? His curiosity piqued, Beast asks him to hear Havok out.
If he hadn’t slept through high school science class, Havok snaps at Iceman, he’d know what happens when two planets get close. The delicate balance of gravity is upset, causing tidal waves, earthquakes destructive forces that make a cobalt bomb look like a cap gun!
What’s that got to do with them? Iceman demands. Havok reveals that right now the Z’nox world is passing the orbit of Saturn. Within 24 hours, it will intercept Earth. They are coming; they are almost here! Last night, a Z’nox craft arrived, its mission to serve as a homing beacon for the mother planet. It landed at the south magnetic pole.
Marvel Girl asks for proof. Do they think he’d make up anything like that? he shouts. His veracity is not exactly Washingtonesque, Beast shoots back. Cyclops warns him he hopes he is telling the truth. Lorna chimes in, defending Havok.
Alex goes on that the aliens aren’t counting on and they have a plan to stop them cold. Whose plan? Angel asks. Alex isn’t bright enough to—Cyclops notes Jean is crying in relief. She understands now, she sobs. She can finally stop pretending…
Havok surprisingly agrees with Angel. He’s not smart enough to formulate a master plan. Only one man is… and his name is Charles Xavier!
A very much alive Professor X wheels into the room and telepathically greets his X-Men. She knew? Scott asks Jean. She admits she did but had to keep it secret. Xavier reveals he ordered Jean’s silence. He had a task which permitted no interruption. These many months he has been secluded in a sub-basement beneath the mansion. Beast points out that they saw his body and buried him. Not him, Xavier replies grimly, rather a brave person… and in the final accounting good.
Flashback / narration:
While engaged in telepathic star scanning, Xavier had learned of the impending Z’nox invasion and was desperately seeking means of countering it, when a stranger slipped into the mansion past all the alarms. Xavier recognized him as the Changeling. The Changeling revealed he had learned he was suffering from a deadly illness and had six months to live at most. He wanted to make them count and make up for some of the rotten things he did. Xavier sensed his sincerity and gave him a task, namely to impersonate Xavier himself.
Xavier explains how he gave a portion of his mental powers to both the Changeling and Marvel Girl and Changeling led the X-Men those few weeks until he was killed by the sub-human Groteskk.
He knows now how Hamlet felt when he saw his father’s ghost, Beast marvels. Angel asks about the aliens. Xavier explains Changeling’s impersonation gave him time to devise a counter attack. He mentally erases the X-Men’s fatigue and for the next hours they have to train as they have never before.
He pressures Iceman to create absolute cold, trains Beast against robots, gets Cyclops to narrow his beam while putting all his energy into it and Marvel Girl to clear her mind as she will have to serve as a transmitter.
Even as the mutants and their mentor are training, another force, namely SHIELD, is preparing to hurl itself against the invaders. Above the South Pole, Nick Fury’s heli-carrier sends warplanes against the alien ship that are instantly annihilated.
Xavier is worried about SHIELD’s intervention and decides they need to act immediately. He briefs the X-Men and warns them to not hesitate in the Z’nox base, but attack with everything they possess. They haven’t a prayer of victory… but might slow them down, Cyclops finishes his sentence. Xavier wishes them Godspeed and goodbye. With that, the X-Men save for Lorna and Professor X leave.
Poleward the Z’nox gloat that the SHIELD attacks are ineffectual, however one projectile does pass their screen. The destroyer missiles home in on the X-Men’s craft but Xavier has constructed it in layers of tough alloy. Each shell is blown away without harm to it precious cargo. Finally, the needle-thin core embeds itself in its objective.
Beast and Iceman peer out to see a huge amphibian creature ready to attack. Cyclops shoots it in the face with all his power.
Elsewhere: news reports reveal disasters occurring in several parts of the Earth. Noted astronomer Dr. Theodore Norton warns of a planet the size of Pluto rushing toward Earth. Barring a miracle, they are doomed!
At the South Pole, the Z’nox agent reports to his leader that the last minor opposition is being eliminated. However, a moment later he is told the enemy has disabled their guardian beast. His leader orders him to dispatch a battle platoon into that area.
The X-Men fight the Z’nox and Beast notes he now understands the training. The Z’nox are exactly as agile as the robots he fought. However, they realize they are outmatched and won’t last long.
Sensing their distress, Xavier orders Lorna Dane to ready herself. Xavier telepathically probes the entire world, searching for people of good will, of compassion, because only this will best the enemy. Some he rejects immediately because to distract them would cause harm – pilots, surgeons… others he rejects because he finds their psyches tainted. And finally those multitudes become joined as one person.
Xavier tells Lorna they must hurry. He can’t keep millions of personalities united. She must direct his mental emanations to the X-Men… Lorna complies.
As Xavier contacts the other X-Men, Angel and Beast using Z’nox weapons are still fighting the aliens. Xavier gives the signal. From the one point on Earth in direct line with the Z’nox homeworld shoots a beam of awesome intensity.
Marvel Girl receives Xavier’s thought patterns, directs them at Havok, who boosts them with his cosmic rays and transmits them to the skull of his brother where they are translated into laser-like optic blasts and aimed at the menacing sky, while Iceman attempts to compensate for the heat which wracks Cyclops.
Those who struggle know not why, only that suddenly they are filled with an all-consuming determination. As the beam attacks, the Z’nox feel images of sympathy and compassion enter their minds, emotions that are anathema to them and cause agony. Realizing these feelings corrode everything that makes them Z’nox, they admit defeat and flee.
Cyclops sinks down exhausted and Xavier releases all those minds that helped. A moment later he collapses and Lorna fears his heroic act may have cost him his life.
Unaware of their mentor’s plight, the exhausted X-Men trudge to their rocket and blast clear off. Behind them, the Z’nox explode their own vessel instead of rejoining their compatriots. The X-Men figure they understood what they could be and could no longer stand being the way they were.