Britt Reid is an 8 years old. He’s being driven to his father’s office at The Daily Sentinel for being suspended. His father, media mogul James Reid (Tom Wilkinson) admonishes him for getting in trouble at school and tells him that he should be done trying to get attention after his mother’s death. Britt tries to explain that he was trying to help a classmate being bullied but James silences him. He takes Britt’s favorite toy and rips it’s head off, tossing it in the garbage telling him that “trying doesn’t matter if all you do is fail”
20 Years Later A mini-fridge is thrown through a hotel window. Britt (Seth Rogen) climbs out to survey the damage and cheers. He’s in a hotel party with a bunch of models and very drunk. He takes a girl home with him and shows her the expensive collection of cars at his house, hooking up with her in each car as they run around the garage.
Across town, Benjamin Chudnofsky (Christoph Waltz) walks into the recently established nightclub of Danny “Crystal” Cleer (James Franco), a meth dealer. He sets his briefcase down next to his chair and watches the 4 bodyguards standing behind Cleer. Chudnofsky tells him his story: He spent his life trying to assert control over all the crime families and he did it. Now he’s just pissed that Cleer went and opened a meth dealing operation on his turf, so he issues Cleer an ultimatum: Sign over his club and work for Chudnofsky or die. Cleer tells Chudnofsky a very detailed critique of his appearance, looks, and style culminating in him telling Chudnofsky to: Get a better name and a better sense of style when he retires. Chudnofsky, clearly annoyed by his lack of ability to strike fear into Cleer, shoots all his men with his double barreled pistol. Cleer begs for his life and Chudnofsky asks what he can do to be more scary. Cleer suggests a cool line before killing people. Chudnofsky leaves and presses a button, blowing up his suitcase and the nightclub.
Britt wakes up with the model from last night and finds a coffee next to his futon. He looks at the leaf pattern in the cup and smiles, drinking it. James walks in and asks Britt if he feels his life has purpose before knocking the cup out of Britt’s hands. Britt tells him that he’s going to go to ITT Tech to fix computers for the rest of his life, a joke which doesn’t go over well at all. James yells at Britt for being front page news on The Sentinel for his antics and tells him to stay out of the news. The model asks him to sign the paper for her and he does. Never Stop The Partay.
James walks in the garden and stops by the roses. Britt leaves to go to another party, and when he comes back there is an ambulance and a swarm of reporters outside his house. The television in the limo tells him that his father died of an allergic reaction to a bee sting. A few days later, a funeral is held and a statue is erected in James’ honor. Britt doesn’t care about anything involved and just wants to leave when the DA Frank Scanlon (David Harbour) stops him and offers to help him out if he ever needs anyone to talk to. Britt goes home and fires the entire staff, but is surprised when his coffee tastes like crap. He asks the maid who is cleaning who makes his coffee and she tells him that would be Kato.
Britt waits outside as Kato pulls up on his motorbike. Kato was James’ garage worker and helped create the coffee machine and the special adjustments to the Reid cars (bullet proof, anti-ramming spikes and re-inflatable wheels). Britt asks Kato what he thought of James and Kato tells him that James was a bit of a dick. They get drunk and decide to do something crazy: Kato drives Britt to the graveyard and Britt cuts the head off of his father’s statue. On the way back to the car, Britt sees a young Asian couple get jumped. He yells at them and the gang chases Britt through the graveyard. Kato sees this and goes to Britt’s aid. Time slows down as he uses martial arts to beat the crap out of the entire gang. The pair run back to the car and start speeding away, only to be pursued by a cop. They decimate the cop car until it crashes and drive back to Britt’s mansion.
In the aftermath of the chase, Britt convinces Kato that they need to take a stand and save people…but with a twist. Britt rationalizes that heroes can be stopped by threatening innocents. Instead of being heroes, they’ll be villains to protect the public by taking care of the real criminals. They set out to make the Green Hornet the most infamous person in the city, but incidentally also make DA Scanlon look ineffective. Britt realizes that without a clear idea of what they need to do to fight crime, they hire Lenore Case as Britt’s assistant, who just so happens to have a degree in criminology and journalism.
Mike Axford (Edward James Olmos), the assistant editor in chief, advises Britt to stop covering the Green Hornet and the crime angle, citing the murder of a former journalist who spoke out against corruption. Britt ignores him and numerous calls from DA Scanlon and continues covering his own exploits. He and Kato target key meth labs run by Chudnofsky and blow them up, leaving calling cards so that Chudnofsky can get in contact with them. Tupper (Edward Furlong), tells Chudnofsky what happened during one of the meth lab raids when the Green Hornet and Kato burned it to the ground using their car, the Black Beauty. Chudnofsky scoffs at him, until Tupper tells him that it was more scary than Chudnofsky. Chudnofsky overreacts and accidentally shoots Tupper. Pissed, Chudnofsky puts a bounty on The Green Hornet, resulting in the murders of 7 random people wearing green: a message Britt takes very badly since he was responsible.
Britt asks Lenore what the Green Hornet would do next, as a criminal, and continues following her advice (start small, send a message and eventually put a hit on the head boss.) Britt attempts to ask Lenore out, but she doesn’t seem interested. She invites Kato over for dinner, which makes Britt jealous. Lenore tells Kato that the Green Hornet will probably be killed in a week most likely invited by the man in charge to a peace summit and then be killed. When Kato returns to Britt’s mansion, Britt tells him that Chudnofsky has sent them an email: He wants to meet. Kato tries to warn Britt, but Britt tells him that he will come up with his own plan.
Heading to the meeting place the next day, Britt insists that he has a brilliant plan but as soon as they arrive Chudnofsky has the Black Beauty pushed into a ditch and buried. Kato blows up the Black Beauty using their missile components, freeing Britt and himself to escape. A firefight erupts and the duo barely escape the attack. They return to the mansion, embittered and begin fighting one another out of frustration. Their fight culminates in the destruction of the living room and Kato almost drowning in Britt’s pool. Britt fishes Kato out with a floatie and fires him. Kato implies that he and Lenore had sex and Britt fires her as well over the phone.
DA Scanlon pays Britt a person visit and asks Britt for a favor: publish only good news about Scanlon’s efforts and Britt will see his own influence increase. Britt is outraged and kicks Scanlon out of his office. He slowly realizes that Scanlon is corrupt and goes to ask Lenore back to piece everything together. Meanwhile, Chudnofsky completes his identity crisis by changing his name to Bloodnofsky and wearing a red leather suit. He and Scanlon contact Kato via email assuming he is the Green Hornet to make a deal: If the Green Hornet kills Britt Reid, he can have half of LA and a million dollars.
Scanlon calls Britt and arranges a meeting at a Habachi grill. Kato arrives and Chudnofsky tells him where to find Britt. Chudnofsky asks why Kato is there instead of the Green Hornet but Kato just says that the Green Hornet is in the Black Beauty pointing to the new car’s weaponry. He punches on of Chudnofsky’s men to assert himself and heads inside the restaurant.
Inside, Scanlon confesses to murdering Britt’s father and aligned himself with Chudnofsky. Britt records all this on a recorder USB. Scanlon is pissed but laughs at Britt, telling him that he’s about to die anyway. Kato cocks the pistol in his hand and apologizes to Britt, pointing the gun at Scanlon. Chudnofsky looks in the Black Beauty and realizes it’s empty: Britt must be the Green Hornet. His men charge into the restaurant and Britt and Kato escape in the resulting gun battle.
Scanlon is pissed and Chudnofsky orders his men into cars: They’re going to chase them and kill them. As they are being chased, Britt tells Kato to drive to the Sentinel’s office building so that they can upload the recording online to expose Scanlon. They crash into the building and evade capture, driving to the elevator in order to make it to the upper offices. The Black Beauty II is cut in half by the elevator and Kato uses front wheel drive to drive through the upper offices. Chudnofsky and Scanlon’s men arrive and the final battle begins.
Britt uses the commotion to check the flashdrive and finds that he didn’t save the file: He has no evidence. Kato dispatches most of Chudnofsky’s men but Chudnofsky gets the drop on him. He begins tough talking Kato, buying Britt enough time to distract Scanlon by throwing the recorder into a pile of debris and punching a few of Chudnofsky’s remaining men out. Chudnofsky attempts to kill Britt, but Kato grabs a table leg, snaps it half and shoves both of them into Chudnofsky’s eyes, killing him.
A SWAT team arrives and begins firing on the remaining men, shooting Britt in the arm as he and Kato retreat to what is left of the Black Beauty II. Scanlon uses his position to get to safety and Britt is dismayed that he doesn’t have evidence to expose him. Kato tells him that they will bring down Scanlon in their own way and drives the car through a window, running over Scanlon and dragging him out with them. They eject their seats and use parachutes to land outside of the city.
The Police hunt for the pair and with Britt wounded, they go to the only person they think will help them: Lenore. Lenore freaks when she realizes that they have been committing crimes following her directive. A cop arrives to ask her if she’s seen the duo but she lies to protect them, realizing that they could land her in trouble. With Britt bleeding out of his shoulder wound and Lenore unable to remove the bullet they come up with a plan…
In the morning, Britt delivers a speech eulogizing Scanlon and the Sentinal. He announces that Mike Axford will be the new editor in chief to help run the paper the way it needs to be run: independently. As he delivers his speech, Kato pulls up in the Black Beauty III and says “The Green Hornet sends his regards”, shooting Britt in the shoulder. Lenore rushes Britt into his limo and the two drive to the hospital flush with success. Kato and Britt later pay a visit to his father's statue and reattach the head as a sign of respect, having realized that he stood for something more than his severe demeanor and vow to continue fighting evil with their antics.
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