Genju, a Japanese inventor, shows his nephew, Shiro, a picture of Firestar.
Shiro says she's magnificent, but Genju tells him that her beauty means
nothing – they need her power! Genju tells Shiro to bring him Firestar –
only their powers together can activate Genju's fusion reactor. Shiro
accepts since his uncle's fusion reactor will benefit all of mankind – but
it won't be ordinary Shiro Yoshida that will bring Firestar to their cause –
it will be Sunfire. Shiro transforms into Sunfire the same way Angelica
transforms into Firestar. Genju says that Sunfire is a mutant exactly like
Firestar, so only he can win her. Sunfire says it will be his pleasure, and
flies to find Firestar.

Left alone with his samurai robots, Genju says that his nephew is a trusting
fool – Sunfire and Firestar will never suspect that they will bring Genju's
fire monster to life. With their unwitting help, Genju will control the most
destructive force on Earth!

In a carnival, Peter Parker is trying to win a prize for his Aunt May. Bobby
Drake and Angelica Jones see a show of Shiro talking about his uncle's
samurai robots. Angelica likes Shiro, and Bobby thinks he looks familiar.

Aunt May goes to take a nap in a helicopter, not realizing where she's
getting into. The pilot doesn't notice her and takes off. Peter's
spider-sense warns him of a danger, and he goes to change to his costume.

Onstage, Shiro Yoshida and the samurai robots demonstrate a new invention of
Genju: sonic swords. The robots use the swords to easily cut through wood,
stone and ice. The cut ice scares Bobby. Angelica notices that the
helicopter is in trouble and alerts Bobby. Peter also sees the helicopter,
and puts on his Spider-Man mask. Angelica and Bobby hide and change to
Firestar and Iceman, and Shiro runs backstage and changes to Sunfire.

Firestar flies and keeps the helicopter in the air. Iceman rides an
ice-slide to the air, but Sunfire flies by, melting the slide, and Bobby
falls. Spider-Man catches him with his web. Sunfire holds the helicopter and
tells Firestar to get the motors going. She does, and the helicopter is
working again. Down on the ground, Peter asks Bobby who's the guy helping
Angelica, and Bobby explains that that's Sunfire – he's a mutant like
Firestar and Iceman – they tangles once. In the air, Firestar thanks
Sunfire, and he introduces himself and says he'll sure they'll meet again,
before flying away.

Bobby tells Peter that Sunfire's uncle is Genju, a wealthy mysterious
inventor. Angelica lands near them and says Sunfire was wonderful. Peter
suddenly remembers Aunt May, and hurries to run and change back. Bobby and
Angelica also change – for them, it's easy.

A few minutes later, Peter runs to the helicopter. Bobby and Angelica are
already there, and Bobby says that Peter changes fast. Peter asks Aunt May
if she's alright, and she says yes – she had the nicest nap.

Shiro finishes his demonstration, as the robots take down a brick wall.
Bobby suddenly remembers why Shiro looked familiar – he is Sunfire. He tells
Angelica, and she asks Aunt May for a big favor.

That evening at Aunt May's house, Shiro thanks Aunt May for inviting him to
dinner. Aunt May says it was Angelica's idea, and Shiro thanks Angelica in
Japanese. Ms. Lion likes Shiro, and licks his face. Shiro asks Peter if he
wants to see Aikido, and he does. They fight, and Shiro easily wins. Shiro
gets a signal from his uncle asking him to return to the company at once,
and he excuses himself and says he has to leave. Angelica asks to tag along,
and Shiro says he'd like that.

At Genju's company, Shiro leaves Angelica in the hall and asks her not to
touch anything while he talks to his uncle. He takes the elevator to Genju,
and Genju, seeing Angelica through a security camera, tells him he should be
spending his time searching for Firestar, not wasting time on a girl.

Angelica doesn't follow Shiro request not to touch anything and touches a
monitor, seeing something she's not supposed to do. A samurai robot with a
sonic sword attacks her immediately, ruining the security camera on the way.
Shiro changes to Sunfire and flies up to help Angelica, not knowing that
there's no need. Angelica switches to Firestar and destroys the robot. When
she hears Shiro coming, she hurries to fly away and hide. Sunfire doesn't
find Angelica or the robot, so he switches back to Shiro. He runs and finds
Angelica, also back to her true form, and asks her what happened. She says
she doesn't know – the robot came at her – she must've fainted. He says
he'll take her home at once.

Later that night, Angelica is sitting in her room, looking through the
window. A big sign written in fire letters on the sky that reads "FIRESTAR"
catches her eye. Bobby and Peter are also seeing it from their room, and
Peter wonders if Angelica is watching. His question is soon answered, as
Firestar is seen in the sky, joining Sunfire. Peter says he thinks it's time
they checked out Shiro and his uncle's company – for Firestar's sake.

Firestar and Sunfire fly through the dark sky together happily. They see a
plane in trouble and hurry to save it.

Spider-Man and Iceman get to Genju's company and enter the elevator. Genju
sees them through a security camera and, controlling the elevator, takes
them through the building.

Peter and Bobby end up next to Genju's fusion reactor. Genju calls his army
of samurai robots, and they hurry to attack the superheroes with sonic
swords. Spider-Man's spider-sense warns him ahead, and he manages to dodge a
sword swing. Iceman tries using ice-made weapons, but the swords cut right
through them. He then tries encasing the robots in ice, but they break free.
The robots surround the superheroes and knock them out.

Sunfire asks Firestar to help him one more time and join him – they'll prove
his uncle wants to help mankind. Angelica tells Shiro she'll join him in
anything, and he leads her to his uncle.

Spider-Man and Iceman are defeated, and Genju is delighted – first them, and
soon all mankind will fall before him. He puts a headgear on Peter to put
Peter into a sonic trance. He approaches Bobby to do the same to him, but
Bobby throws ice in Genju's face. A robot tries attacking, but Bobby freezes
its arm and breaks it, before escaping on an ice-slide.

Sunfire tells Firestar to wait for him while he goes in and tells his uncle
she agreed to help them. She agrees, and Shiro flies in, finding his uncle
and robots near a defeated Spider-Man. Confused, Shiro asks Genju to explain
and tells him he brought Firestar. Genju simply orders his nephew to find
Iceman and capture him before he'll ruin everything. Sunfire does as told
and flies away.

Iceman ice-slides through the building, but stops when he sees Sunfire
standing in front of him, ready for battle. Bobby tells Shiro that it's his
uncle he wants to fight, but Shiro thinks Bobby has no reason. Sunfire
attacks with fireballs, and Iceman defends himself with and ice-shield.
Iceman tries attacking with ice, but Sunfire melts it and heats the room.
Iceman knows he can't let Shiro's heat melt him down, so he freezes the
ceiling and the ice falls on Shiro. Sunfire uses his heat to fight Bobby's
ice, and rains fire over Bobby. Bobby responds by encasing Shiro in ice, but
Shiro melts the ice. The two mutants continue countering each other's
attacks until Genju sneaks up on Iceman and puts a sonic headgear on him.
Bobby faints, and Shiro protests against his uncle's method. Samurai robots
arrive and drag Bobby away. Genju tells Shiro to come after him – they must
prepare for Firestar.

Firestar joins Sunfire and Genju, and Genju explains that his fusion reactor
will create limitless energy for the world, and Firestar and Sunfire's
combined powers will ignite it. Firestar accepts, and the two mutants enter
the fusion reactor as Genju enters the control room. A robot reports through
a video screen, and Angelica sees her friends tied in the back. She wants to
leave, but Sunfire grabs her arm and uses his heat. She tells him to stop
before she'll burn up, but he tells her to simply use her power and keep up
with him. Having no other choice, Firestar uses her power too, activating
the fusion reactor. Firestar asks Sunfire why he's making her do this, but
before Shiro can answer, Genju's evil plan comes to life – a giant fire
monster bursts out of the fusion reactor.

Sunfire and Firestar fall to the ground. Shiro tells his uncle that the fire
monster is stealing all their power and begs for help, but Genju just laughs
madly and asks his nephew to join him in his conquest of mankind. Shiro
rejects, saying this is wrong, so Genju orders his robots to lock the two
powerless mutants with the others.

When they get to Peter and Bobby, a robot puts a sonic headgear on
Angelica's head, but Shiro manages to fight his robot and steal its sonic
sword. Shiro releases Angelica, and she releases Peter and Bobby.

Genju flies out of the building with metal wings, followed by his fire
monster. He orders his monster to destroy and burn the city, and it does.

Spider-Man says they have to go and stop the monster, but Angelica tells him
the monster drained her and Shiro of their power – they are useless. Peter
says there's got to be enough energy in the reactor to restore their powers,
if it doesn't kill them first, and Sunfire agrees. Sunfire and Firestar
enter the reactor as Spider-Man and Iceman take over the controls. The
reactor explodes and Bobby panics, but then Angelica and Shiro step out – it
worked.

The only problem left on the way out is the remaining robots. Spider-Man
gets a sonic-sword, but can't activate it. Iceman creates a large
ice-shield, but then Peter destroys it with the now working sword. Bobby is
confused, but Peter says he has a plan and tells Bobby to cover the floor
with ice. Bobby does as told, and then Angelica and Shiro melt the ice into
water. Peter tosses in a torn electric wire, and the robots explode.

The fire monster continues destroying the city, with Genju encouraging it.
The Spider-Friends and Sunfire get to the scene and realize that this is
gonna be a lot harder than the robots. Firestar gets an idea, and tells the
others.

Iceman fills Spider-Man's web with chunks of ice, and the Spider-Friends
part ways to work on Angelica's plan. Spider-Man starts by throwing ice at
the monster with his web, and Genju orders the monster to destroy
Spider-Man. The monster follows the instructions and starts chasing Peter.

Firestar and Sunfire get to the sea and start whirling rapidly in circles
above the water, until the water get sucked into two tornado-like shapes.
Iceman ice-slides by and, just as Firestar and Sunfire let go, freezes the
water to two large ice pillars.

Spider-Man keeps web-spinning across the city, luring the monster and
wondering how he got talked into doing this. At the last second before the
monster catches him, Angelica and Shiro fly by and carry him away. The
monster keeps following the superheroes until it gets lured to right between
the ice pillars. Once in position, Firestar and Sunfire leave Peter with
Bobby and melt the pillars. The water pour on the monster, and its flames
are put out until the monster is no more. Genju cries out in despair, as
Shiro flies to him and takes him away.