It's business as usual for the X-Men, as the four male X-Men are training in the Danger Room. It's the Beast's turn, and he has to balance on a cable, into a tunnel, with a machine blasting force beams from above. He masters the task with ease, making a witty comment that neither sleet nor snow may slow him down.
Iceman thinks to himself that maybe some ice could do the job where sleet and snow fail, and he covers the cable that his teammate is balancing on with a thin layer of ice. Balancing barefooted, Hank immediately senses the difference and leaps upward, saying that Bobby seems to be reverting to his days as a practical joker.
Upon landing again, though, Hank slips and runs head-first into one of the force beams. While Bobby is rather glad that the Beast didn't seriously injure himself, he also notes his friend's anger and tries to downplay the incident. Hank is not in forgiving mood, though, and plans to give Iceman a headache that will make his own seem decidedly pale by contrast. Before Angel or Cyclops can intervene, all four X-Men suddenly fall silent, as they receive a mental command from Professor Xavier, calling them to his study.
On their way through the hallway, they run into Marvel Girl, and are actually surprised to meet her there, as they believed Jean to be working together with Xavier on some secret project. Asked about it, Jean replies "Yes and No!" which Scott considers to be a typical woman's answer if he ever heard one. Still, he reminds the X-Men that they have no time to waste, and within moments, they are all assembled in Xavier's study.
The Professor explains that he summoned the team because of some astonishing news he just learned, which might soon shock the world – Frankenstein’s Monster has been found. Iceman is surprised, saying that he thought it to be a myth and something to be seen on the “Late Late Show.” Xavier goes on that he isn’t talking about a movie monster, but the eight-foot humanoid referred to in the novel by Mary Shelley. He always believed the book was based on an actual occurrence, and now is sure of it. Hank and Jean comment to each other how grim and intense the Professor is, though he overheard and asks them to be silent.
(partially in flashbacks)
Xavier reveals that, while he was engaged in some mental experiments, he accidentally intercepted a radio message from New York harbor that told about a mammoth being found near the Arctic Circle, entirely immobile and encased in solid ice. It had been found during a polar expedition financed by New York's City Museum, and led by a Dr. Powell. Unsure whether the creature in the ice was truly human or not, he arranged for him to be transported to New York. Xavier projects a mental image of the creature’s face, and the X-Men begin to understand why he thinks him to be the so-called monster created by Victor Frankenstein. The monster has a bulky head, grim eyes, wrinkled, gray skin and screws are sticking out of the sides of his neck.
When Iceman wonders what the monster was doing up north, the Professor reprimands him for apparently not having read the novel, even though the students were assigned to do so last spring. According to the book, Victor Frankenstein pursued his creation into the Arctic region until he died and the monster boarded the ship to his creator’s lifeless form, and then he leapt overboard and vanished from sight. Citing the closing words of the novel, “He was soon borne away by the waves and lost in darkness and distance!” Xavier reveals that he always suspected the monster to have really existed, though he never thought he might show up again.
When Cyclops asks how all this may concern the X-Men, Marvel Girl tries to provide an answer and asks their mentor if he believes Frankenstein's monster to have been a mutant. He denies that idea, although the redhead is not far wrong. Xavier suspects that the "monster" was in truth a super-powerful android and, by examining him, he might be able to prove that his unknown creator must have been a mutant possessing a highly advanced brain.
Next, Xavier tells his students that time grows short, as the creature has already been taken to the museum where they plan to defrost him - which could be rather dangerous to the staff. Warren asks if he truly believes the monster could be still alive after more than a century, and Xavier replies that, if he truly is an android, then he could not “die.” As the team prepares to leave, Angel says that, if this works out, he'll be looking for the yellow brick road the next time he goes on vacation.
Meanwhile, at the museum, Dr. Powell is already preparing to defrost the creature, when he is suddenly surprised by another scientist. Powell's colleague is surprised to find him there, as the government told them not to perform any experiments on the giant until they approved of them. Powell doesn't care about these orders, though. He is convinced that it is his right to examine the creature first - after all it was he who found him. As he begins manipulating the temperature inside the transparent casing holding the block of ice, Powell's colleague points out that it's dangerous and brings up the possibility of the creature still being alive. The scientist considers such talk nonsense and asks to be left alone so that he can continue his work.
Outside, Professor Xavier and his students arrive in front of the museum. They have changed into civilian clothes, not wanting to draw any attention. While the guard at the door recognizes Xavier and greets him friendly, he tells him that the museum is already closed for the night and that they would have to come back the next day. Not wanting to be further delayed, the Professor gives Jean a telepathic order, and she telekinetically slams the guard against the door, knocking him out. The X-Men hope that, by the time he wakes up, he'll think that it was an accident.
Suddenly, the mutants hear a crashing noise from inside the building, and they fear that they have come too late. Scott orders the others to change into their costumes fast and follow his lead.
Inside the lab, the creature has indeed broken out of the chamber he was held in, and the lab equipment is in ruins. He says "Human worms! You have served... your purpose! You have brought me... to a new land! Now stand aside... or I crush you like fleas!" His arms raised triumphantly, Dr. Powell shouts, "He lives! The monster lives!” until he begins to realize that the creature is heading smashing through the wall and about to escape - obviously endangering the citizens of New York.
Right then the X-Men arrive on the scene, and Angel starts the fight with a frontal assault. However, the eight-foot creature knocks him out of the air with a single pinch in the face. While doing so, the monster makes a comment about Warren's colorful costume, saying that he looks like the ones he most despises. The giant announces that he will be pursued into the land of ice a second time, and the Beast tries to use the monster's gloating to his own advantage, attacking him from behind. Yet, the creature is unimpressed and doesn't even budge. Just like Angel before, Beast is sent flying with a simple blow. Cyclops is the next to try his luck, and fires an optic blast at the monster.
Meanwhile, in another part of the building, the curator of the museum is calling the police. Although he has no idea who responsible, he knows by the noise that someone is tearing up the place and asks the police to hurry. He also grabs a pistol and loads it with a few bullets.
The creature belittles Cyclops for attacking with no weapon that could really harm him, though it also recognizes that he is more dangerous than the two other X-Men who attacked first. Scott fares slightly better than his two teammates, at least his optic beams are able to slow the monster down somewhat. Unfortunately though, while walking backwards, Scott trips over some debris and knows that he can't dodge the creature's next punch. Marvel Girl comes to the rescue, levitating her boyfriend out of harm's way with her telekinesis.
Jean voiced her fears of anything bad happening to Scott, but he interrupts her, saying that they still have a powerful opponent to deal with. Cyclops, having used optic beams against him, the monster decides it is only accurate to do the same, and releases two glowing beams from his eyes. Not having expected this, the four X-Men are taken by surprise and are all rendered unconscious. No longer anyone blocking his way, the monster sees no reason to remain there and leaves through a hole in the wall, feeling that there is something he must do elsewhere.
Fortunately, due to their many hours of training, none of the X-Men are seriously harmed, and Hank already comes around by the time the museum curator enters the damaged part of the building. Seeing only the four costumed X-Men, he believes them responsible for the destruction, and points his gun at Hank. Before he can shoot at anyone, though, he is immobilized by a thin layer of ice covering him, courtesy to Iceman, whom the Professor ordered not to become engaged in the battle at the last minute.
Several minutes later, Xavier's Rolls Royce is speeding through the night, but Cyclops wonder how they could find the monster, as he doesn't register on their portable Cerebro device. Xavier replies that they have to find him, and that's why he sent the Angel ahead to do some scouting. Indeed, from above, the winged X-Man soon spots the creature's trail of destruction.
Following the demolished cars and buildings, Warren finds the trail to be leading towards the docks. Xavier picks up that bit of information mentally, and knows they have to reach the harbor as fast as possible. He has the X-Men drive to the Pan-Am building, where he uses his mental powers to command the officials into lending the mutants a helicopter and forget about the whole matter. The professor says they'll return the helicopter later, but first they have to stop the android.
Following Angel’s thoughts, Xavier steers the helicopter to a southbound freighter on the ocean. Along the way, Iceman asks if he’ll get in on the action this time, and Xavier replies that he had him stay back because of a premonition last time, but in this second encounter the X-Men will need all their powers. Right after landing on deck of the freighter, the X-Men have to deal with the ship’s crew first.
Unaware of the creature hiding aboard, the sailors are suspicious of the mutants’ intentions and, in their new costumes, they don’t even recognize them. With several guns pointed at them, the X-Men have no way but to fight their way through, it being for the crew’s own protection after all. Eventually, Marvel Girl reaches the captain and convinces him to grant the team permission to search the ship. Just to be on the safe side, though, Xavier says he’ll mentally keep the crew immobile.
Xavier orders the X-Men to split up, with Marvel Girl and Iceman staying above decks, and the others searching below. Making his way through the freighter, Cyclops thinks to himself how bizarre this adventure is – Frankenstein’s monster no myth but reality. He wonders if it was truly created by a mutant, and if they somehow could reason with the creature and make him use his powers for the benefit of mankind.
In the meantime, the Beast has reached a chamber full of tropic-bound crates. His instincts tell him he is on the right track, though he is also aware of there being numerous hiding places between the crates for the monster. Suddenly one crate next to him crashes, the creature having leapt at it from his hiding spot. He is rather angry that “the costumed ones” are still following him, and declares that he will destroy the X-Man this time. The agile Hank manages to dodge Frankenstein’s monsters first punches, though.
Above, Jean, Bobby and Xavier have heard the crashing sound, and know it can only mean that one of the X-Men has found the creature. The Professor senses that the monster is drawing closer and warns his X-Men to stand ready. Only an instant later, the steel floor is ripped open by the creature. Beast leaps through the makeshift hole and joins his teammates, with the monster close behind him.
Suddenly, a rope noose drops down on the giant creature, tightening itself around his torso. Angel threw the lasso and, after attaching it to one of the freighter’s crane, he tells the Beast to pull the monster up, so that he’ll be helpless. Easier said than done, though, and while the Beast has enough leverage, the monster still doesn’t move. Amazingly, his feet generate some sort of magnetic field, so that he sticks to the deck. Eventually, the rope snaps under the strain, and the X-Men haven’t achieved much but to further anger the monster.
As the creature heads for some barrels, Iceman thinks that he can’t stand back any longer, despite the Professor’s direct orders. He uses his ice powers to quick-freeze each barrel that Frankenstein’s monster is tossing, who seems to be somewhat startled by an opponent using ice as a weapon. Having become the creature’s number one target, Iceman wonders if he should try to put him in cold storage, but Jean enters the battle and reminds him that the Professor warned him not to.
She quickly helps her teammate, temporarily holding the monster’s arms with her telekinesis so that he can’t throw the barrels any more. The creature won’t let himself be stopped by that, as he stamps with one foot with terrific force, sending out a shockwave that makes Jean topple and causes Iceman to be slammed against the frozen barrels.
Cyclops enters the fight, blasting his optic beams at the monster from behind so that he can’t absorb the rays and send them back at Scott. All the while, the X-Men’s field leader regrets that they haven’t found a way to reason with the monster and wonders who the other “costumed ones” are that he keeps mentioning. Beast comes to aid his teammate, swinging on some rope and punching Frankenstein’s monster in the back. However, the creature reacts quite fast and dislodges the entire post that Hank’s swinging rope is attached to. Once again having successfully dealt with an opponent, the monster says that not even all costumed ones who still abound in this world would be able to stop him from reaching his goal.
At this point, an overwhelming thought permeates the ocean air. Xavier uses his telepathy and sends out a message to the monster. He says that he is not one of the costumed ones he hates so much, but he is the one who commands them to attack, and that’s why the creature should try to destroy him and not them. The monster is taken aback somewhat; after all Xavier looks the most helpless of them all, so why should he challenge someone as powerful as he other than to seal his own doom? The Professor knows that Frankenstein’s monster might be right, for even his psi-bolts would only delay him. Still, he has a plan, but for that he needs more time, so he telepathically alerts Cyclops to buy him some time.
Scott does as told, and blasts at the monster with his optic rays once more. Again his attack is rather useless, and the creature rips out the part of the ship’s hull that Cyclops was standing on. Even worse, Scott’s has spent his all power with that last try and can’t help Xavier anymore. He only hopes that the Professor knows what he is doing. The creature turns to Xavier again but, as he tries to reach the telepath, he finds an invisible force holding him back. It’s the Professor’s mental bolts. Unfortunately, though, the android has no human brain for him to control, so Xavier’s power won’t help him for long. His only hope is that his final telepathic call is successful in the next few moments.
It is, for at precisely that instant, Frankenstein’s monster is encased by a thin layer of ice. It’s Iceman’s doing, who Xavier mentally revived during the brief delay that Cyclops brought. The creature shouts that ice is the thing it hates most, as Iceman keeps pouring on more and more ice. The monster fight back, though, and the ice begins to crack, but Bobby strains his ice-forming powers to the upmost. For a few tense moments, the outcome of the battle could go either way, though eventually the android’s inner systems can’t handle the cold any more. Guided by Xavier, Bobby uses more and more of his ice, and then quickly creates a shield covering the X-Men.
He obeys, and not a moment too soon, for Frankenstein’s monster explodes. After the smoke has cleared, the X-Men gather at the creature’s remains. Iceman now understands that the one thing the monster could not stand was intense cold and that was the reason why Xavier asked him to stay back. He apologizes for almost fouling up the Professor’s plan by attacking too soon. Xavier says it doesn’t matter anymore and reveals that, in the last seconds, he managed to probe the android’s artificial brain, thus learning the true origin of “Frankenstein’s monster”.
He tells the astonished X-Men that the monster was not from Earth, but the creation of some alien race from a far-off tropical planet, which passed Earth approximately 150 years ago. Before approaching Earth’s population themselves, the aliens decided to send an experimental android to them and, depending on how he would be received, they would have established personal contact.
Jean says that this would make the creature the first inter-stellar ambassador, and wonders what went wrong. The Professor responds that evidently the android malfunctioned and instead became a menace: the aliens corrected their error and pursued it to the polar regions, where, since it was created in the aliens image, he was helpless. When the monster was revived, it acted upon his instinct of survival, and it attacked the X-Men because their costumes somewhat resembled the colorfully garbs of the aliens. The only questions that remains is how Mary Shelley learned of all this, but probably they’ll never know.
(the next day)
At Xavier’s school, the X-Men read about the incident in the newspaper, which quotes the captain of the freighter as having no idea what has caused the minor explosion near the harbor. The Beast finds it rather bad that their mentor had to make the whole crew forget about the battle with the android. Xavier says it doesn’t matter, after all their purpose is to safeguard the world and not to search for personal glory.
In a dimly lit shack, hidden somewhere in a forest, Scott Summers realizes that he was somehow drawn, if not controlled, to come there. Seeing a middle-aged man in the shack, Scott asks who he is, and how he controlled him, but the man interrupts, saying that he will do the talking. After introducing himself as Jack Winters, the man explains that he is a mutant, just like Scott himself, whether he knows it or not.
Scott answers that he doesn't know what that's supposed to mean. After all, he is only a runaway teenager. Winters once again interrupts, letting Scott know that he can tell when he mentally connects with another mutant brain - and that's exactly what he just did. Jack Winters even correctly guesses that Scott is the mutant teenager from the news. Realizing that it's no use to play dumb any longer, Scott admits that he is that boy, and that his eyes shoot out some sort of force bay that can only be held in check by the special sunglasses that he is wearing.
Noting that Winters doesn't wear such glasses, Scott is curious whether his power is just a mental one, but his mysterious host says that they'll have to continue their conversation later, as they are about to have company. Jack douses the lamp, and points his hand at Scott, who is still confused by the fact that Winters can tell there are people outside just by receiving their mental vibrations.
Next, he begins to feel rather strange, almost as if he is dissolving and fading into his atoms, and Jack confirms that this is exactly what's happening. Winters assures Scott that his followers won't find him, and that he'll be joining him in a few seconds. Once that Scott is entirely gone, Winters focuses his power on himself and also vanishes away. Not a moment to soon, for a few moments later, two policemen enter the shack. They wonder how it can be empty when they had heard voices from outside, and the lamp is still warm either.
Meanwhile, Professor Xavier has returned to his secluded mansion in West Chester county, and switches on a device of his own creation, called Cyberno. With this machine, Xavier hopes to find the location of the mutant teenager, who by now could have reached the New Jersey-Pennsylvania border. Suddenly, a flash of light indicates that the machine has found Scott Summers, only it registers a second, far stronger force in the same region. Xavier understands that while looking for one mutant he has found two, and put on some headgear that allows him to use his power in combination with the machine. However, just as he was about to get an exact reading of the mutants' exact location, the contact breaks off, almost as if the two mutants had suddenly vanished off the face of the planet. The professor is determined to find them, though.
(some hours later)
Jack Winters and Scott Summers materialize inside a nuclear power plant that isn't too far away from New York. Scott can hardly believe that Winters has the power of teleportation, and the older man explains that he can only travel short distances, which is why they had to hop a train to get close enough to the plant to jump inside.
The teenager asks what it is they are going to do inside, and why Winters brought him along, to which Jack replies that Scott is asking too many questions. He asks the teen to trust him; after all, they are both mutants. Scott is persistent, though, saying that this doesn't mean one bit that he will help Winters if he has something shady up his sleeve. Pointing out that Scott is already guilty of breaking and entering anyway, he decides to finally let him in on his plan.
(flashbacks, over the course of the last couple of months)
Jack Winters was working at the nuclear power plant, but not making enough money to pay off some gambling debts of his, which is why one night, he secretly broke into the lab complex. Waiting for hours until the guards had passed, he tried to steal some radioactive materials, wanting to demand a ransom from his bosses for their safe return. However, Winters was inexperienced with such materials, and he accidentally broke a flask of isotopes which exploded in his hands.
He managed to escape without being caught, but afterwards had to spend a few weeks in hospital where his radiation burns were treated. The hospital staff took pity in him, thinking that the radiation might cause permanent damage to both his hands and his brain. Indeed, Jack had a hard time coming to terms with his accident, and he actually wished that he had died. However, several days later, he began to feel different, his brain was tingling as if it was picking up radio ways and, when he removed the protective gloves he had been wearing ever since his injuries, Winters found that his hands hand been turned into pure diamond.
Jack Winters concludes his origin, saying that Scott can guess the rest. Soon, he discovered that his brain was picking up thought waves when anybody was near. He takes off his gloves, showing the startled teenager his transformed hands. Diamond being the hardest known substance, Winters easily smashes through a girder of pure steel, just to demonstrate to Scott what he could do to him, if he won't do as he says. Scott is unsure what to do and quickly realizes that Winters did not befriend him at all, but only needs him as an ally in his plans. Still gazing at his diamond fingers, Jack explains that he believes a heavier dose of the radioactive material from his accident would transform his entire body into diamond, and also possible increase his brainpower as well.
Suddenly, the two mutants hear a telepathic voice, telling Jack Winters to stop his mad quest for power before it is too late. These thoughts being so overwhelming, Scott surmises that it must be another mutant observing them, and Winters agrees for once, as he already had a feeling they were being shadowed. Checking their surroundings, Winters spots a man in a wheelchair coming down a hallway towards them, and he orders Scott to use his eye-beams on him. However, the troubled teenager knows that at this close range he'd murder the bald man, and he doesn't want to become a murderer, no matter what Jack might do to him.
Listening to Scott's inner struggle, Xavier considers himself lucky to have found them before the evil mutant gained too much of a hold on Scott. Although he knows that it's risky to confront them alone, he thinks he has no other choice. Winters isn't pleased by his supposed ally's disobedience, and attacks Xavier by himself, just to show Scott what will happen to him if he doesn't do as told. Jack rushes forward, and Xavier tries to attack him with a mental bolt, but the villain's own mental powers protect him. As the professor wonders if he is doomed before he truly begun building his dream, Winters declares that he is “about to become the first victim of Jack O' Diamonds.”