Plot

When Mark Grayson finally inherits powers from his superhero father, it's a dream come true. But there's more to being a hero than just choosing a name and costume.

High schooler Mark Grayson discovers that he has inherited flight, enhanced strength, and speed from his superhero father, the legendary Omni-Man. As he creates a new superhero identity, an unexpected assailant attacks the world's premier superheroes, the Guardians of the Globe.—Gislef

Two guards are outside the White House, upcoming Superhuman Evasion Training, and how one of them will be gone that week. One of them, Steve, discusses how his son was a problem but has turned his life around and how he's taking his son to London on vacation to show how he and his wife appreciate their son's hard work

The villainous Mauler Twins break up through the pavement and bicker about which one of them is the clone of the original. As the White House's weaponry opens up on them, one of the Twins points out that since the President is targeting them, the plan was to kill him publicly. They open fire and destroy the weaponry, and Steve shoots at them and orders them to surrender. He hits one Twin in the eye, hurting him, and the Twin prepares to kill him.

The Guardians of the Globe drop out of the sky and Immortal fights one while Red Rush gets the guards to safety. War Woman has the soldiers evacuated, and the wounded Twin attacks her. Darkwing evacuates civilians, and Green Ghost uses her powers to render some civilians intangible so they're not hurt by debris.

Martian Man and Aquarus fight a Twin breaking through the White House wall, then the heroes go inside to clear the building. The Twin throws a civilian into the sky, and Darkwing snags her and drops to the nearby sidewalk. When the Twin throws a tank at a nearby building, Darkwing and the woman are caught in the collapse. The hero gets the woman clear using his grappling line, but is still trapped. Omni-Man arrives and lifts the tank off of Darkwing, who destroys falling debris landing on Darkwing and flies off on his hover platform.

Immortal tosses more soldiers clear, and Omni-Man flies overhead and grabs them. Once the White House is clear, the Guardians and Omni-Man unite and fight the Twins with no civilians to be harmed. The heroes take out the two villains.

At home, Mark Grayson is in the bathroom on the toilet reading a comic book. His mother Debbie comes in, looking for soap. Later downstairs, Mark watches a newscast about the White House, and tells Debbie that his father Nolan--Omni Man--is there with the Guardians fighting the Mauler Twins. Debbie isn't impressed, and Omni-Man flies down and comes in. He goes to show, and Debbie insists on kissing him first. Mark is disgusted that his parents are talking about sex in front of him.

As Mark prepares to go to school, he overhears his parents talking about going to Berlin for brats. When he complains, Omni-Man says that Mark has school and he can go when his powers kick in. Mark points out that his powers haven't kicked in yet, and Omni-Man assures him that on his home planet Viltrum, powers kick in by the 18th birthday.

As Mark leaves, he sees Omni-Man fly off overhead. He tries to fly but fails, as a passing postman stares.

At school, Mark and his friend William Clockwell talk about the Twins' attack. Mark defends Omni-Man, who is considered "the underdog". A bully down the hall, Todd, is harassing another student, Amber Bennett. Mark insists on getting involved, and tells Todd to back off. Todd beats him, and Amber kicks Todd in the groin. The bully runs off, and Amber thanks Mark for trying to help her.

That night at Mark's job at BurgerMart, he's hauling out garbage. He tosses one bag in, but it flies off into the sky from his over-powered throw. Mark realizes that his powers have manifested.

Later, Mark goes home for dinner and Nolan arrives. Mark tells them that he's getting his powers, and Debbie kicks Nolan under the table until he expresses some enthusiasm. Nolan tells Mark that he'll start training him in the morning.

That night, Mark tries to sleep but can't. He remembers when he was young, and Nolan told him that he really comes from Viltrum, an alien planet. Viltrumites possess super-strength and speed. When they come of age, they venture out into the galaxy to help less-advanced races. Nolan relocated to Earth to be its soul protector, met Debbie, and they eventually married and had Mark, who is half-Viltrumite.

In the past, Nolan explains the changes Mark will go through when he hits puberty, including getting powers.

In the present, Mark remembers Nolan telling him that he's going to be able to fly. He gets out the window onto the roof, braces himself, and jumps off. Mark hovers in mid-air,, then flies off into the sky. An airliner almost hits him and Mark flies out of Earth's atmosphere, passes out from lack of oxygen, and falls back to earth. He wakes up just as he crashed into the street in front of his house.

The next morning, an exhausted Mark wakes up at 6 am. Omni-Man comes in and gets Mark, and they fly up into the sky. Mark's father explains about Mark has to focus on flying since he's a novice, and leads him away. Omni-Man notes that Mark is better at flying than he should be, and wonders if he's been doing late-night practice. He has Mark land, but Mark can't slow down and crashes into the earth. Omni-Man then trains Mark in how to fight, and continues giving his son tips. He punches Mark in the chest, knocking him to the ground, and apologizes for hitting him harder than he intended. Omni-Man tells Mark that if he wants to be a superhero, he needs to be prepared for anything.

Mark and Nolan return home, and Mark goes up to his room. Nolan tells Debbie that he pushed Mark far and it's what Mark needs, and snaps at Debbie when she questions him. Debbie asks Nolan what's gotten into him, and Nolan apologizes and says that Mark getting his powers so late changes things. He wonders if their lives would have been better if Mark hadn't gotten powers at all.

The next day at school, William notes that Mark isn't very talkative. Todd comes up, grabs Mark, and slams him into a locker. Mark invites Todd to hit him, and when Todd does so, Mark shrugs him off and tells Todd to hit him again and again. Todd does so and Mark doesn't flinch, and Toss calls him a freak and walks off. Mark tells William that he needs something to punch.

Later, Mark makes an improvised mask and flies through the nearby city, and hears gunfire. Titan, a stone-skinned villain, and two robbers are running from the guards. As Titan grabs his two associates and jumps over a gate, Mark flies up and slams Titan back. Mark hasn't come up with a superhero a name yet, and Titan beats him. Mark finally slams Titan down the alleyway and knocks Titan out, so Titan drops his armored skin.

Omni-Man flies up and tells Mark that he looks ridiculous, and suggests they get out of there. They fly to a rooftop and Omni-Man points out that Mark did a lot of damage, and he's not ready to be a superhero. Mark tells his father to hit him now that he's ready for it, and when Omni-Man refuses, Mark tells him to let him prove he can take the pain and is ready to be a superhero. The teenager tells Omni-Man that he wants to do what he does, and Omni-Man hugs him and assures him that he will be.

The superhero flies off, telling Mark to follow him. Omni-Man flies his son to the basement of a tailor shop at a mall, where Art Rosebaum is working. Art tells Mark that he secretly makes supersuits, and Mark says that he wants something "iconic". The tailor asks what name Mark has decided on, and tells Mark to think about it and get back to him.

That night at home, Debbie goes outside and finds Mark crashing into the earth. He explains that he was practicing his landings, and Debbie tells him that he needs to sleep. Debbie orders Mark inside and he tells her to make him. His mother asks if his being strong is important, and Mark says that it's important. Debbie tells Mark that she's there for him if he needs to talk, and figures that she's boring and Nolan isn't. Mark worries that he's nothing special, more like Debbie than Nolan, and wonders how he can live up to Omni-Man. Debbie tells her son that he just needs to be the greatest him, not the greatest Omni-Man, and assures him that the greatest Mark is enough.

The next day, Mark and Nolan float in the sky and play catch. Nolan wonders why Mark seems distracted, and Mark finally tells his father that he's scared that he can't handle superheroing. His father throws a ball around the globe, and Mark catches it. Nolan explains that along the path of being a superhero, Mark might have to do things he doesn't want to do or think he can't do, and it's okay to be scared. Nolan tells his son that he has to push through his doubts, and if he can then he'll be fine.

Mark says that he can do that, and tosses the ball around the planet to his father. Nolan tells Mark that he is invincible. Getting an idea, Mark goes to Art and tells him his new superhero name.

Soon, the costumed Invincible is sitting on a crane above the city. Invincible then flies across the city and up into the stratosphere, then flies down to the city and sees cannon blasts coming from a villain, Kill Cannon. The police officers' bullets are unable to penetrate Kill Cannon's armor, and Invincible flies down and punches the villain through a building. Invincible continues punching Kill Cannon down the street.

Red Rush, in his secret identity as Joseph, is having a picnic with his girlfriend Olga. He speeds away to tie up a super-villain, Kursk, then comes back. Joseph says that his perceptions are also accelerated, but being with Olga is a gift. His Guardian emergency alert goes off , Olga says that he understands, and Red Rush speeds off.

Immortal is battling his nemesis Bi-Plane over Denver. Bi-Plane threatens to blow himself and the city up, and Immortal throw the villain into space. The hero's emergency alarm goes off and he flies off.

On his throne, Aquarus is bored. He gets the emergency alarm and swims off, thrilled to have some action

In her civilian identity as Holly, War Woman meets with her assistant Connie. Connie describes they have a third quarter coming up where they should make money for the company. Holly would rather help the world, and gets the emergency alarm. She changes to War Woman and flies off.

Martian Man is practicing his expansion powers and increasing their strength. His emergency alarm goes off and he flies away./

As a photographer, Green Ghost gets the emergency alarm and calls it a wrap, then transforms and flies off.

Darkwing is capturing two robbers He gets the emergency alarm and leaves.

The Guardians gather at their mountain base, and wonder who sounded the alarm. Red Rush, with his heightened perceptions, pushes Immortal out of the way as Omni-Man attack the latter. The other heroes attack Omni-Man in self-defense, and Red Rush gets Aquarus out of the way of Omni-Man's next attack. When Red Rush moves in to punch Omni-Man, Omni-Man grabs him and despite the superspeed blows to his chest, crushes Red Rush's head.

Martian Man entangles Omni-Man while the others attack the latter. Omni-Man smashes Darkwing's head in on the floor, then throws him at Green Ghost. She turns solid to catch Darkwing, and Omni-Man drives a fist through her head. Omni-Man uses Green Ghost's body as a shield against Aquarus' water blasts, while Immortal figures that they have to have to stop Omni-Man no matter the cost.

Omni-Man disarms War Woman, takes her mace, and crushes Aquarus' skull. Martian Man entangles Omni-Man while Immortal and War Woman beat Omni-Man. Omni-Man rips Martian Man's heart out, killing him, then drives a fist through Immortal's chest and breaks War Woman's neck. Immortal wonders why Omni-Man has turned against them, and Omni-Man chops off Immortal's head. Bloody and beaten, Omni-Man collapses unconscious.