The citizens of New York are well accustomed to clamorous sounds, but nothing could prepare them for the ear-splitting reverberations, which suddenly bombard them one autumn morning. Whether they are walking in the streets or driving in their cars, all hear a deafening noise – the source is a man flying above them, wearing a green and yellow costume and a strange headband with a symbol consisting of three circles on it. All the New Yorkers would see though, that is if they weren’t busy covering their ears, would be a blur, as the man is flying too fast to be spotted.
He descends towards an art gallery and, slightly varying the sonic vibrations that keep him aloft, he shatters the plate-glass window that is separating him from the prize he seeks. The figure, calling himself the Banshee, lands next to some passed-out bystanders, who have been rendered unconscious by his scream. Talking to himself, he gloats that he only needed a fraction of his sonic powers to place an entire city block in a trance. He then reaches out and takes a painting from the shop’s window, the prize he came for. Admiring its beauty, he agrees with the description he read in today’s tabloid, it truly is “a landscape of incredible tranquility, of the utmost serenity.”
Mere moments after the Banshee takes to the air and flies away, the effect of his shriek wears off and the people are coming around. Mr. Jones, the owner of the art gallery, wonders what happened, the last thing he recalls is him displaying the latest French imports to Mrs. von Brahmin. The woman, too waking up, is the first to note the damaged window and alerts Mr. Jones to it. Soon after, a police officer is at the scene. Upset, Mr. Jones reports that despite thousands of dollars in art treasures lying in the window, the mysterious thief took only one painting of a Gaelic landscape. When asked why they all passed out, Jones answers that he honestly doesn’t remember.
Meanwhile, at Xavier’s mansion in Westchester, the Professor and his X-Men pursue activities on their own, watching a radar-like machine. The Angel says that the Professor used his mental power to increase the duration of the Mimic’s abilities, but can they be sure its effects are permanent. No, Xavier replies, that’s why he ordered Calvin Ranking to fly in ever increasing circles away from the school, so that he can monitor his progress on the M-indicator. While Cyclops remains silent, Iceman and the Beast snicker that they wouldn’t mind if their new teammate just kept going and going. Xavier reminds his students to put their personal feelings for Calvin Rankin aside, for he has agreed to help them against the mutant menace, which Cerebro recently detected. Suddenly, a red light flashes on the M-indicator, which means that the Mimic has exceeded the limits the Professor placed on him. He is leaving the control area.
Xavier telepathically contacts his newest students that he is in danger and orders him to return, but Calvin knows better. He thinks that Xavier’s mind-blast worked perfectly and he now has permanently absorbed the others’ powers. However, even as he speaks, his wings begin to shrink and he has problems staying aloft. As the Mimic plummets towards the ground, he cries for the Professor to help him. Xavier remains calm and mentally advises Calvin to use his remaining power to turn around – it’s his only chance. With only a few inches between him and the trees below, the Mimic manages it and gets within the range of the other X-Men, their powers returning to him. The truth sinks in that he will always have to stay within a certain distance, but then again he is still as powerful as the rest of the team together.
At the school grounds, the rest of the team awaits the Mimic’s return. The Beast, clinging to the mansion’s wall, is the first to spot Calvin in the skies, and he says that there is no doubt he’ll regale them with an account of his hair-breadth escape. Xavier tells Hank not to underestimate the Mimic; he may be a bit headstrong, but basically he is a fine person. Bobby though thinks that calling Calvin Rankin headstrong is like comparing a hurricane to a slight breeze.
Calvin lands and addresses the Professor on his performance; sure he was doing great. The telepath answers that the test proved that they succeeded in increasing the range of his absorption talent, but wants to know why Calvin exceeded the proscribed limits. Mimic answer: because he felt like it, and it’s no big deal, as they have learned what they wanted. The Professor says that they’ll continue this discussion later, but now he needs to check Cerebro for any records on new mutants. He asks Cyclops to accompany him, who answers that he’ll follow him in a few minutes.
Once Xavier is out of sight, Scott asks the Mimic to have a word with him in private. Calvin asks him “What’s on your little mind?” Scott replies that maybe the Professor doesn’t feel like calling him down, but as deputy leader of the X-Men, Calvin needs to learn to take orders as well as give them. The Mimic, unimpressed, tells Scott that he is just jealous for he had to pass on leadership of the team to him, and after all it was not him but Scott who wounded the Angel with his power. Scott lets it slide for now, but gives Calvin a final warning: he is riding for a fall.
Meanwhile, in a well-concealed hideout in the city, a bulky figure called the Ogre is operating several computers and machinery. He is in excitement, as the long hours of watchful waiting have finally paid off – the systems have located the secret headquarters of the X-Men. The Ogre knows that Factor Three will be pleased, for now they can proceed as planned. He decides to inform his partner the Banshee of his discovery and climbs down a ladder into another room of the base. He welcomes him back, asking where he has been to anyway, and complains about his partner smoking a pipe.
Banshee responds that the Ogre obviously has no sense for the finer things in life, like this painting for instance. Seeing the stolen artifact, the Ogre is taking aback. He gets angry with his partner, saying that his looting an art gallery endangered their true mission. The Banshee, not really caring, says that “loot” is a rather plebejan term. He would prefer that he “procured” the painting for someone who would truly appreciate it, namely himself.
After learning that the Ogre located the X-Men though, the Banshee promises to fulfill his part of the mission, and the Ogre needs only to worry about his own. While saying this, he wants to stuff himself another pipe, but his pouch of tobacco is empty. The Ogre angrily walks away to make final preparations, as they will strike within the hour. Banshee tells him he will be ready, though thinks to himself that he needs to get some new tobacco before.
Not much later in midtown Manhattan again, the Banshee’s wail is heard and the people in the streets are placed in a hypnotic state, while Banshee searches for a tobacco shop he remembers in this vicinity. Indeed he finds it and, upon entering it, jokingly says to himself that he has trouble being served, so he is forced to help himself. While he stands before a board full of important tobaccos to choose from, wondering which to pick, he fails to notice that he is observed. The building’s janitor spots “that long haired fella in the costume” and thinks that he must have knocked out the clerk while he was in the storeroom. If only he had heard him in time, he thinks, he might have stopped him, but unfortunately he forgot to wear his hearing aid. (unaware that this is what prevented him from being rendered unconscious like everyone else).
The janitor quietly sneaks out of the store and locks up behind him, locking even the security gate. He becomes aware of rather many people having been knocked out, but he decides that he can’t bother about that right now, as he needs to find a police officer. No sooner has he left, than the Banshee has picked his choice and, trying to leave, finds the exit blocked. It’s no problem though, as with his power of sound he can cut through metal thicker than this. Banshee takes to the air, knowing that he needs to hurry now, not wanting to be too late for their attack on the X-Men.
At Xavier’s mansion, Cyclops and Xavier are checking the automatic recording of Cerebro’s latest readings, and they find evidence of brief mutant activity in Manhattan only a few hours ago. Just as they are about to discuss that reading, Cerebro flashes on, reacting a second time to the same mutagenic signature. The intensity of Cerebro’s reaction shows them that the mutant in question must be utilizing his power in frightening degree, not even Magneto made the machine react that strong. Suddenly, though, the light begins to flicker and dies. Unfortunately, there wasn’t enough time to pinpoint the location of the signal and it seems that their enemies have found a way to avoid being discovered by Cerebro. Scott suggests to ready the X-Men for leaving towards Manhattan, but Xavier tells him not to, as his calculation of recent weeks showed him that the mutant’s next target will be their mansion and they need to prepare against this attack.
At the same moment at the campus of Metro College, Jean Grey is enjoying an Indian summer afternoon. Sitting in the grass with her fellow student, Ted Roberts, a radio playing music next to them, Jean asks why all of a sudden Ted is so strangely pensive and thoughtful. He brushes it off; it’s just the letter he received from home. As always, it’s full of praise for his older brother, Ralph, who turns everything he does into a success, while he is just a mere college student and can’t compete with that. Jean tells him he doesn’t need to compete, but Ted interrupts her, as there is a news bulletin on the radio. Jean curses to herself, as she had hoped she could finally learn why Ted drives himself so hard, but then she too listens to what the radio moderator has to say.
He reports of the two mysterious mental blackouts which have struck entire sections of Manhattan midtown and that, on waking from their trances, the victims could remember nothing but a weird high-pitched sound. The only unaffected person was a half-deaf janitor who is the only one able to describe the costumed criminal responsible. However, apparently the only stolen items were a painting and some tobacco. Jean wonders if this is the great mutant menace the Professor seemed so worried about, though with these minor thefts it doesn’t seem likely. Then again, it could have been test runs, part of some deadly plan. Ted says he thinks there is more to this story and that someone should look into it, to which Jean comments that she has a hunch someone will.
On a private-owned dock, the walls of a small, prefabricated building fall away to reveal a mysterious, metallic rocket-shaped cylinder – the secret base of the two villains. At precisely the same instant, a fire breaks out on another dock across the bay and several abandoned warehouses catch fire. The Ogre announces that the pyro-projector is working perfectly and, with everyone’s attention at the fire, nobody will notice their strange looking headquarters. Next, he operates the many monitor screens to tune in with the news. They report of the fire, and also of many people who have become inexplicably terrified by the sounds of police-sirens and fire alarms. All of them were in midtown during the two mental blackouts that occurred that day.
Hearing this, the Ogre gets angry. “Did that miserable mutant venture outside the capsule twice while I was busy? If so, Factor Three shall learn of his folly!” He descends into the bases lower level, where the Banshee is once more smoking. Seeing his partner, the Ogre thinks that it’s no use to ask him about the incident and, instead, he tells him that it’s time to get their plan into motion, for now they shall capture Professor X, the leader of the X-Men. As a sliding section of dock becomes a ramp and the capsule slides into the river, the Ogre thinks that the world’s freedom is doomed, but it will not become aware of it until it is too late.
At Xavier’s, the X-Men are busy operating the mansion’s many machines. Mimic and Cyclops are adjusting the defensive devices, while Iceman and Beast are calibrating Cerebro, hoping to register their enemies’ signature. Xavier and the still-wounded Angel observe them quietly. Every communication is made telepathically through the Professor, as the mutants are wearing special ear shields under their masks. The tired Angel goes up to his room to get some sleep and, not much later, Cerebro goes off. Despite the special-treated wax in the shields, Xavier can still hear the machine, which means it must be a very strong mutagenic signature. Beast and Iceman look at the machine’s read-out and realize, in shock, that it means their foe is right upon them.
Indeed, a sonic scream crashes the window of the office and the Banshee flies in, wailing. His power of sound is much greater than the X-Men predicted and their ear-shields are ineffective against it. They all hold their heads in pain, trying to keep the noise out, but it’s no use and within minutes all present fall unconscious. The Banshee stops screaming, briefly gloats about his easy victory and switches off Cerebro, as its alarm is still ringing. He then contacts his partner, the Ogre, through his wrist-radio, telling him that he is finished and it’s now up to him. The Ogre agrees and orders Banshee to quickly leave before the Mimic can absorb him and his immunity to his own power.
While Banshee departs, the Ogre flies in, using his jet-equipped boots, for he is no mutant and all; his abilities are based on his mechanical equipment. Within minutes, the bulky man emerges from the mansion again, carrying a securely bound Xavier across his ample shoulder. As he walks away with his prisoner, he recalls how Factor Three carefully plotted to the smallest detail for the telepath's capture and the irony of the world being unaware of the Professor’s role as leader of the X-Men and his incredible powers. And it’s those powers that Factor Three will use to conquer Earth.
Suddenly he trips over a branch hovering a few inches above the ground, courtesy to Marvel Girl. She tells the foe that, instead of boasting, he should have been counting, or else he wouldn’t have missed the fact that the female X-Man was not present during the Banshee’s attack. With the Professor lying on the ground, still out cold, the Ogre gets up and announces that he won’t be thwarted by one lone female, even a super-powered one. He blasts at her with his wrist repello rays and, though Jean levitates out of it’s way, she can still feel the terrific force of the beam. She tries to dodge behind a tree, but a second blast cuts her off.
Just as the Ogre is about to deliver a final ray, Cyclops, Beast and the Iceman storm out of the mansion coming to her rescue. Fortunately, their ear shields protected them enough that they recovered much quicker from the Banshee’s wail than anticipated. Now they are eager to show the Ogre what they think of overstuffed baddies trying to capture the Professor. However, the Ogre apparently robs them of their vengeance, as he uses his rockets boots to propel himself out of harms way. Circling above the X-Men, he manages to blast at them with his wrist-shooters. Some X-Men, though, are capable of arial combat too, as the Mimic intends to show. He flies in above the Ogre and leaps onto his back. Getting overconfident once more, the Mimic already proclaims victory, but the Ogre turns in mid-air and lands a punch in the latest X-Man’s face.
The five X-Men regroup, Shaken and bruised, while the Ogre seems to be unharmed. While his teammates are bantering with their opponent, Cyclops thinks that he needs to get on one side, as he can’t blast at the Ogre with him standing directly in front of the incapacitated Xavier. He doesn’t get the time to act according to his plan though, as the Ogre decides to use another gadget. Pressing a button in his belt, he demonstrates that the circles on his suit’s chest are more then mere ornaments; they are powerful flashlights, dazzling the teenage mutants. Now he has more than enough time to get away with his prisoner, before they can continue to fight him.
However, just like his students, Xavier too is awake again and despite, his hinds being tied behind his back, he manages to roll around and make the Ogre trip over him. The foe realizes that he can’t fight them all at once, especially as, in the next seconds, Xavier will be recovered enough to use his mental powers. He presses some sort of stud in his glove, signaling the Banshee that he needs his assistance.
Only instants later, again the deafening noise is heard and Jean, who witnesses it for the first time and is wearing no shields at all, cries out in pain. The others realize that this is not the same sort of scream as before and the Banshee now upon them confirms their suspicion. This sonic modification makes his voice seems like a solid thing and the X-Men are all knocked backwards, though they maintain consciousness. At least the distraction provides the Ogre his chance to get away. Though his flight path is somewhat shaky, his jet-boots having been damaged by Jean’s trick with the branch.
While the X-Men free their mentor and take him back inside, the Banshee returns to the villains’ concealed capsule in the nearby woods. He has overused his powers today and his sonic vibrations had barely enough strength left to fly back. However, he thinks it doesn’t matter for, as soon as the Ogre returns with Xavier, their mission is at an end. Then again, a few minutes later, the Ogre returns alone without the X-Men’s mentor. He blames it on the Banshee and his inability to use his hypnotic pitch and render the mutants unconscious a second time. He even goes as far as suspecting his partner of sabotaging the mission on purpose. Banshee calls him a fool. He would never deliberately endanger their purpose and he should know the reason why. In turn, he blames the Ogre for their failure, who now puts the dispute aside and urges to begin a second assault, once Banshee’s power has recharged.
In the mansion, the X-Men are making preparations of their own, installing further security devices and equipment. The Mimic demands to know why these criminals are after Xavier, but he tells he will explain later, when he can be more certain of the facts. For now, it’s important to focus on the matters at hand. He reveals that, during the battle, he was able to mentally probe the ear-shields built into the Ogre’s helmet, which are coated by a substance he can duplicate, after learning its makeup. He tells the X-Men to adjust the new stuffing beneath the paddy ear-shields under their masks and they comply. Again, they are now forced to commune telepathically with each other.
A few minutes later, Cerebro again responds to the Banshee closing in on the mansion and Xavier alerts his students to their stations. Banshee flies in through the crashed window and is confident to defeat them, as his powers are back at their peak. However, even using his highest frequency hypnotic wail, the mutants are unaffected. He realizes that they must have found a way to shield their ears and decides to retreat before he is captured. Too late, though, as the Mimic actives a lever that causes a steel-mesh net to be lowered into Banshee’s flight path, trapping him. While doing this, Mimic already feels a tingle, a certain sign that he is starting to copy his foe’s powers.
The ensnared Banshee struggles desperately to free himself, but his vibrations do not shatter the specially treated net ... so far. Before the material eventually breaks, the Professor tries to mentally soothe him, but the Banshee is vibrating so fast that he can’t focus on him. Mimic then uses his newfound sonic powers to strike the trapped opponent, slowing him down to a certain degree. The Beast quickly leaps in and fires a stun gas pellet at the Banshee. It explodes on impact and, finally, the Banshee is knocked out.
The Mimic thinks about the Beast looking rather smug and that, without his power of duplication, the Banshee couldn’t have been defeated. However, the Professor telepathically tells him that this is not the time for grandstanding. The X-Men hurry to secure the prisoner before he might awaken. He is strapped into a pressure suit and placed into a vacuum chamber. Once inside, he soon comes around and realizes he is trapped. The Banshee is being given just enough oxygen to breathe, but not to vibrate free. “Correct,” Xavier tells him, establishing telepathic contact with the unique mutant.
He then asks Cyclops to fetch an extra oxygen tank from the cellar lab and the group’s former leader obeys. However, once in the basement, Scott can’t help but to notice a heavy oaken door, which has been locked ever since they returned from their last vacation. Strangely, Xavier never told them why. Thinking that he’ll find out sooner or later, and this not being the time to solve the mystery, he gets back to his work.
A floor above, Xavier sends the Mimic out to reconnoiter, to see if he can locate the Ogre. Calvin happily takes on the assignment, as he was starting to go stir-crazy in the mansion. Hidden in the bushes next to the front door, the Ogre sees him take to the air and decides that with the most powerful of the X-Men gone, now is the perfect time to attack. He sneaks into the house and manages to reach the lab unseen. He brought a larger, gun-shaped version of his repello ray with him and fires it at the people in the lab. In the last instant, the Professor warns all present and orders them to scatter, though they are still hit by the brunt of the force and knocked over.
Alone left standing, the Ogre approaches the vacuum chamber containing the Banshee, talking to himself that he has failed Factor Three and they no longer have any use for him. Though the chamber is soundproof, Banshee can read his partner’s lips and realizes that he intends to kill him. He takes aim, and ...
The repello rifle is blasted from the Ogre’s hands by a powerful optic beam. Cyclops has returned from the basement and the Ogre quickly escapes through the window. The X-Men, slowly coming around, ask their mentor whether they should go after him, but Xavier tells them it was a set-up. Had Scott not returned, he himself would have protected the Banshee with a mental bolt. Right now, the Mimic is on the Ogre’s trail. Indeed, as the mutant teens rush to the window, they witness their unwelcome member using the powers absorbed from the Banshee on the Ogre, who in return fires his repello rays again. The Mimic erects a sonic shield and then uses all his powers in combination. Angel’s flight, coupled with Banshee’s speed, propel him forward with uncanny speed, and the Beast’s strength allows Calvin to smash the chest control panel of the Ogre’s suit.
The other X-Men watch them both going down, still fighting, but the Mimic uses the Beast’s agility to gain the upper hand. Suddenly, they hear the sound of crashing glass behind them, the vacuum chamber has been shattered. Just as they prepare to battle the Banshee another round, Xavier mentally orders his students to fall back. The sonic mutant vibrates really fast until he gets rid of the pressure suit he was strapped in. Though now free, he doesn’t attack the assembled mutants but powers down. Cyclops wonders why that is so and the Professor promises to fill them all in, as soon as they remove their ear shields and he uses his mental bolt on the Banshee’s headband.
Once done, the Banshee happily exclaims that he is finally free. Ripping off the headband, he explains that, while it looked like he and the Ogre were partners, it was actually the case that the Ogre dominated him through an explosive device hidden in that headband, which could have been activated by remote control. Iceman says that if they had known, they could have freed him sooner, when he was unconscious, but the Professor objects. His mental probing had revealed that the headband would have exploded, had they tampered with it. Only with the Ogre’s control panel destroyed has the danger has ended.
Now with the Banshee no longer being their foe and the Ogre captured, the X-Men have time to wonder why they tried to capture their mentor. Xavier says that he knows part of the answer – it has to do with Factor Three. One of the X-Men comments on that sounding rather lame for a criminal group, but Banshee tells him that this is no joke. Factor Three is the most dangerous secret organization on Earth. They have the means to conquer the planet ... or even to destroy it.