http://www.viewwave.com/ Britt Reid (Seth Rogen) is the 28-year-old son of James Reid (Tom Wilkinson), publisher of the Los Angeles newspaper The Daily Sentinel. Britt is an irresponsible playboy who throws wild parties to embarrass his father, a stern disciplinarian who has always been disappointed in him. However, his attitude changes when James is found dead from an allergic reaction to a bee sting. After the funeral, Britt fires the staff aside from his maid and Kato (Jay Chou), James' mechanic and a skilled martial artist.
Britt and Kato get drunk together and, upon agreeing that they both hated James, visit the graveyard to cut the head off James' memorial statue as payback. After they succeed, they see a couple being mugged, and rescue them. Britt and Kato are themselves mistaken by police for criminals and chased through the streets, but Kato evades them and he and Britt return to the mansion.
Britt convinces Kato they should become crime-fighters who pose as criminals in order to infiltrate the criminal underworld, and also to prevent their enemies from using innocents against them. Kato agrees, and develops a car outfitted with several gadgets and weapons, which they call the Black Beauty. Britt plans to capture Benjamin Chudnofsky (Christoph Waltz), a Russian mobster who is uniting the criminal families of Los Angeles under his command, and whom his father was trying to expose. To get Chudnofsky's attention, Britt uses the Daily Sentinel as a vehicle to publish articles about a "high-profile criminal" — the Green Hornet.
Britt hires Lenore Case (Cameron Diaz), who has a degree in criminology, as his assistant and researcher, and uses her unwitting advice to raise the Green Hornet's profile. Britt and Kato blow up several of Chudnofsky's meth labs, leaving calling cards so Chudnofsky can contact them. Throughout all this, Daily Sentinel managing editor Mike Axford (Edward James Olmos) fears this single-minded coverage will endanger Britt's life, and District Attorney Frank Scanlon (David Harbour) frets over public perception that he cannot stop the Green Hornet.
Britt asks Lenore out, but she rebuffs him and instead invites Kato to dinner, making Britt jealous. Kato learns from her that mobsters often offer a peace summit to rivals in order to get close enough to kill them; Britt then tells Kato that Chudnofsky has offered them such a meeting. Kato tries dissuading him, but Britt, feeling overshadowed, follows his instincts. Chudnofsky tries to kill them, but they survive thanks to Kato's quick thinking.
Barely escaping to the mansion, Britt and Kato argue and fight, and Britt fires both Kato and Lenore, whom he believes are in a relationship. Kato receives an email from Chudnofsky on the Hornet's calling-card email address, offering $1 million dollars and half of Los Angeles if he kills Britt. Meanwhile, Britt discovers Scanlon is corrupt, learning that he tried to bribe James into downplaying the level of crime in the city in order to help his career.
Scanlon invites Britt to meet in a restaurant, where he reveals he murdered Britt's father. Kato arrives, and instead of killing Britt, he attacks Chudnofsky's men, allowing him and Britt — whom Chudnofsky deduces is the real Green Hornet — to escape. They head to the Daily Sentinel, where Britt intends to upload a recording of Scanlon's confession onto the Web — and belatedly discovers he did not manage to record it. Chudnofsky and his men follow the duo there, where a firefight ensues. Kato ultimately stabs Chudnofsky in the eyes in self-defense and Britt guns him down. A SWAT team appears and fires at the Green Hornet and Kato, while they use the remains of their nearly demolished Black Beauty to run Scanlon out the 10th-floor window, killing him. The Green Hornet and Kato flee to Lenore's house, where she learns their secret identities and that she has been the accidental mastermind behind the Green Hornet's plots. She is furious, but nevertheless helps them hide from the police and tends to Britt's shoulder gunshot wound.
The next morning, Britt promotes Axford to editor-in-chief and stages being shot in the shoulder by Kato, further establishing the Green Hornet as a threat (and allowing Britt to get treated by professionals in a hospital). Later, the two weld James' stolen bust back onto his memorial statue. Now with Lenore to aid them, Britt and Kato vow to continue protecting the law by breaking it.