- Natt Wolff as Sam Alexander / Nova
- Josh Duhamel as Jesse Alexander
- Ron Pearlman as Titus (voice)
- David Tennant as Rocket Raccoon (Voice)
- Vin Diesel as Groot (voice)
- Tom Hardy as Ronan the Accuser
Two men fire at Kree soldiers, the human one suggests retreating to gather more numbers, while the other, a cat looking man, suggests they fight on. The human is given no choice but to leave for backup, but the cat-person shoots at him, claiming to the Kree that he is a double agent. He misses the man, but saves his own life by joinging with the Kree. Meanwhile the man flies off into space, accepting that he is now hunted.
Modern day. Suburban Oklahoma
Sam Alexander was a rebellious teen, annoyed with his poor background, being brought up with a factory worker for a mother and a plumber for a father. Jesse, his dad, was the village drunk, he was always drinking to get through his struggles. he would always tell Sam and his younger sister stories of his days as a Nova, a intergalactic 'police officer'. As Sam grew up he realised who his father was, and how his stories were simply ramblings of a broken man.
In the present, Sam opens the door for his dad, wraps his arm around his dad and walks him to the garage, where he sleeps after a night of drinking. In there was a bed, random drawings of space, plumbing tools and a locked chest. Sam didn't know what was in there.
When skating to school he was stopped by a few of his schoolmates, including Jackson, the son of the local bar owner. He claimed his father smashed an expensive statue in his bar and he needed Sam to pay for it. Now. Sam had no choice but to run, in which a foot chase ensued. He was caught up by Jackson and his friends, when Sam through a punch at Jackson. They proceeded to fight briefly before Sam was knocked down. Cuts to a flashback montage of the many stories Jesse told his son as a kid. He wakes up, black eye and a broken rib. He gets out his phone and sees a picture of his mum and dad. Cut to flashback of Sam arguing with his mother over his father's state. She tells Sam how he wasn't always like this, and that he sacrificed a lot to raise a family. He slams the door and we return to the present. He throws his phone into the bushes and leaves for home, missing school.
He returns home to his dad's garage, slams open the door, shouting at him for what he had done. His Dad wasn't there. Sam's Mum saw his black eye and asked what happened, only to realise her husband wasn't there. He often went out without warning, but they both knew something different about this one. The chest was unlocked and empty.
Sam ran into the night, checking all the bars in town. He was still mad at his Dad. he couldn't find him anywhere. he checked the last place he could think of, an old cabin in the woods, a place his uncle lived at. Sam was crossing a rope-bridge over a river to get their when it snapped and he fell a large distance down to the river below.
He awoke a few weeks later in a hospital bed. Sam had no memory of what happened to him. He lay awake in the hospital bed when his cracked phone began to ring beside him. Someone must have found it in the bushes. He picked up. "Hello?" - - "Hi. Sam. Meet me in the garden in five. I'm a friend of your father." the phone hung up. Dazed and confused, Sam changed into his clothes and made his way slowly outside. In the Hospital's garden one of the trees moved and a Raccoon jumped down from it's 'shoulder'. "Hi, I am rocket. This Groot. Your father saved us from a little trouble once, so we owe him in return." - - Sam stood in disbelief. "You're not real. you. you're just an image of these painkillers. HELP!" He began shouting frantically. Groot and Rocket panic, when Groot picks him up and hangs him upside-down. Rocket approaches an upside-down Sam. "I am the realest there it. If you wan't your father back you better realise that real quick."
Sam followed Rocket and Groot into the forest. They explained that the stories his father told him were true, that he really was part of the Nova. They explained were bounty hunters, but ultimately just 'good people trying to make a little cash' so Jesse Alexander let them free after capturing them, but they would be in his debt. This was the debt, to deliver something to Sam. They revealed a helmet, something that had been stored in the chest all these years. They had broken it out upon hearing Jesse's distress signal. They gave it to him and told him he'd work it out. They entered their ship in the forest and quickly flew off into space while he was distracted by the helmet. Annoyed, he had more questions than answers, so he kicked the helmet across the ground. It lit up blue all-of-a-sudden. Sam had thought this was all a bad dream, but he felt a feeling of power coming from the discarded helmet. He reluctantly put on the helmet, feeling a whoosh of power as a suit materialised over his body. He began to float above the ground.
After coming to terms with his powers, he is given basic training by Rocket and Groot who explain the concept of the Novas to him. They next visit an alien outpost where Sam puts his powers to work on a squadron of blue-skinned aliens. Upon beating the group of aliens, the three of them begin hacking the computer to check upon the blue aliens' intentions. They turn out to be an army of Kree, one of the two armies battle for control of the galaxy. The kree are leading an army into this sector to create an outpost in the area. The army is lead by Titus, a feline-like terrorist and ex-nova, one who previously worked alongside Jesse Alexander, explaining his rushed leave from Earth. Then Sam, Groot and Rocket are suddenly captured by more Kree forces and taken to a ship. Groot and Rocket are locked away while Sam is invited up the bridge of the ship.
There he meets Titus, who wanted to see his ex-partners son, the newest nova. He shows him their weapon, the ultimate nullifier, a weapon of mass destruction that could destroy the entire solar system. He interrogates him as to his father's whereabouts, but Sam does not know. As Titus turns his back, Sam attempts to escape but is beaten in a one-on-one fight with Titus. Meanwhile Groot and Rocket escape (An activity they excel at) and help out Sam as he is going to be killed. They are captured again, while Sam is given some time to escape.
He flees to Xandar, where he meets Nova prime and the Nova army, all of them who have no records of his father's location, after further lessons and training. He also find out the truth about Titus's betrayal to his father that lead him to leaving the Nova corps. Nova finally convinces Nova Prime to take an army with him to stop Titus using the ultimate Nullifier. A battle ensues between the Nova and the Kree, with many casualties. Sam manages to find the mother-ship and get on without dying. He goes to the prisoner bay and frees Rocket and Groot, who make their way to an escape ship. He then fights Titus again, using his anger and his new training to fight him one-on-one.
They continue to fight when Rocket and Groot crash a ship through the front of the ship, hitting Titus. In a moment of panic and Bravery, Sam grabs the ultimate nullifier and activates it, throwing it as far into the Kree fleet as possible. He ordered the Nova to retreat, and Rocket and Groot fly the ship away under Sam's orders. The ultimate nullifier is activated, creating a giant black hole that begins to suck in the entire Kree fleet. Sam is about to escape when Titus grabs his ankle, with the two fighting as they are falling through the ship. The end up hanging onto a large pole coming of the ship, with Titus grabbing his ankle again. The ship flies closer inwards as Sam has no choice, he blasts Titus with his energy blast, sending him to his death.
With Sam accepting he had avenged his father, he let go to die in peace, when Rocket's ship caught Sam and managed to just fly away in time. Then it stopped, the Kree were gone, and the ultimate nullifier was left to fly around space. Sam and the Nova returned to Xandar where he was given a heroes welcome, and though they could still not find his father, Sam was appointed an official Nova and was assigned to protect the milky way. Rocket and Groot were rid of their previous crimes and debts, leaving with a new ship called the Milano, they felt good for once in their life. Sam would eventually return home to tell his mother of his achievements and his guilt over not finding his father. Despite this, he knew he would not give up.
In an after credits scene was a alien metropolis. A man walks through a jail, passing Jesse Alexander looking beaten in a cell. He continues to walk through the hallway up to the bridge where he exclaims "My master, Titus's fleet is gone. A Nova destroyed it. Just a kid. He used the nullifier against them." there was a pause. "What will you do". The larger man rises and picks up a large hammer. "I will accuse him". The camera zooms out to show a fleet three times the size. Cut to black.
- Ronan will likely survive the movie to go on to lead a Kree invasion in either The Avengers, or a future Nova movie.
- Nova opens up the cosmic side of the marvel universe, with concepts like the Nova, Kree, Skrulls etc. to all be used in future movies.
- Groot and Rocket are both future Guardians of the Galaxy. Their mentor-like relationship with Sam is part of their journey to becoming heroes, something that would eventually lead them to joining the Guardians.
Jaga took this project because he wasn't really a fan of Nova. Compared somewhat to a mixture/rip-off of Spider Man and Green Lantern, he looked to mix up some of the story to make the story slightly different to those properties. He preferred Sam Alexander's story to Richard Rider's due to being slightly less cliché. he also felt that spinning this film has given a great opportunity to open up future plot points in the universe, including a possible villain for the avengers movie.
Sam's personality was largely changed for the movie to more of a rebellious teen. This move was done to differentiate himself from other teen-heroes like Spider Man.