Eight years after the events of the first film, Miami Police Department (MPD) narcotics division detectives Marcus Burnett and Mike Lowrey are investigating the flow of highly-potent ecstasy into the city. Their surveillance of boats coming in from Cuba leads them to a Ku Klux Klan meeting and drug drop in a swamp docks outside Miami. The subsequent raid on the Klan members proves to be a disaster; malfunctioning radios delay back-up, causing a firefight when Mike accidentally shoots Marcus in the buttocks, while the Klan members are revealed to be mere small-time buyers and not the distributors of the ecstasy. The incident leaves Marcus to further question if he still wants to partner with Mike, while Mike fears that Marcus may discover his new relationship with Marcus' sister, Syd.
In 1968, Frank Lucas, the limo driver-turned-right-hand man of Harlem gangster Ellsworth "Bumpy" Johnson, inherits Johnson's gang when Johnson dies of a heart attack. Disliking the new, flashy gangsters of the neighborhood, Lucas decides to take control of Harlem's crime scene.
In Fall 1995 in Detroit, Jimmy "B-Rabbit" Smith Jr. (Eminem), a young and unhappy blue-collar worker from a poor family, struggles with various aspects of his life. He has moved back north of 8 Mile Road to the rundown trailer home in Warren, Michigan of his alcoholic mother Stephanie (Kim Basinger), his little sister Lily (Chloe Greenfield), and Stephanie's abusive live-in boyfriend Greg (Michael Shannon). Although encouraged by his friends, who hail him as a talented rap music artist, Jimmy worries about his potential as a musician, particularly due to his lack of confidence. This caused him to panic during a rap battle one night at a club called The Shelter, and leave the stage humiliated.
In 1986, Eric "Eazy-E" Wright enters a crack-house to sell drugs, but, it is soon raided by the police, who gain entry into the house via a battering ram. Eazy escapes through the house's rear window. Later, Eazy goes to a club with Lorenzo "MC Ren" Patterson to see friends Andre "Dr. Dre" Young, O'Shea "Ice Cube" Jackson and Antoine "DJ Yella" Carraby, who perform the song "Gangsta Gangsta", while Eazy and Ren stand in the audience. After Dre leaves the club, he is arrested after breaking up a fight involving his brother, Tyree. Eazy bails him out the next day. The next morning, Dre talks to Eazy about investing money into a start-up record label, in order to record a track that Cube has written. Cube and Dre want rappers H.B.O.(Homeboys Only) to record the track. Eazy agrees to fund the project. After a conflict arises during the recording session, H.B.O. leaves and Dre convinces Eazy to perform the track. They record and release "Boyz-n-the-Hood". Jerry Heller approaches Eazy and asks if he can be their manager. The group accepts Heller's offer. While performing "Dopeman", they garner the attention of Bryan Turner, a producer at Priority Records, with which they sign. Afterwards, N.W.A commences recording their debut album, "Straight Outta Compton", with Heller. During one of the sessions, they are harassed by some police officers. Frustrated by the situation, Cube writes "Fuck tha Police".
LouAnne (Michelle Pfeiffer), a discharged U.S. Marine, applies for a teaching job in High School, and is surprised and pleased to be offered the position with immediate effect. Showing up the next day to begin teaching, however, she finds herself confronted with a classroom of tough, sullen teenagers, all from lower-class and underprivileged backgrounds, involved in gang warfare and drug pushing, flatly refusing to engage with anything. They immediately coin the nickname "White Bread" for LouAnne, due to her race and apparent lack of authority, to which LouAnne responds by returning the next day in a leather jacket and teaching them karate. The students show some interest in such activities, but immediately revert to their former behavior when LouAnne tries to teach the curriculum.
The story begins in traditional video style, as several of the film's characters are recorded and asked a series of questions about why they dance. The film then cuts to Moose (Adam G. Sevani) and Camille (Alyson Stoner) who attend New York University. Moose is majoring in electrical engineering after promising his father that he would not dance anymore. While touring the campus, he sees a pair of Limited Edition Gun Metal Nike Dunks worn by Luke Katcher (Rick Malambri). Moose follows the shoes and then accidentally stumbles upon a dance battle, where he beats Kid Darkness (Daniel Campos) from the dancing crew "House of Samurai". Luke takes him back to his place, an old warehouse converted into a club. Luke shows Moose the House of Pirates, his dance crew, where he later teams up with them to compete in the World Jam dance contest against their rivals, the House of Samurai dance crew. But then, Jacob (Keith Stallworth), a member of House of Pirates, informs Luke that the warehouse will be put up for auction if the overdue rents are not made.
In Baltimore, Maryland, Andie West (Briana Evigan) pursues her big dream of becoming a street dancer. Following the death of her mother to cancer, Andie lives with her mother's best friend, Sarah (her guardian), but in reality, Andie feels like she does not belong anywhere. Although she is doing poorly at school, it is her dream for dancing that brings something special into her life. She trains with her dance crew, the "410" (pronounced four-one-oh, as in the area code for Baltimore), to keep the title of the illegal competition, 'The Streets.' Sarah is aware of the crime and harassment by the 410 and after an argument with Andie, she decides to send her to live with her Aunt Alice in Texas, but Andie, fed-up with Sarah's arguments, runs away.
Marcus Burnett (Martin Lawrence) and Mike Lowrey (Will Smith) are best friends and detectives in the narcotics division of the Miami Police Department. One night, $100 million of Mafia seized heroin is stolen from a secure police vault. This is a major blow to Burnett and Lowrey, because it was the biggest drug bust of their careers. Internal Affairs suspects that it was an inside job with corrupted police officers and warns the rest of the department that if they do not recover the drugs in five days, the narcotics division will be shut down.
The movie begins on Ocean Drive in Miami, Florida. A flashmob, later identified as 'The Mob,' shuts down Ocean Drive by cutting off the streets with retro convertibles and dancing on cars to music blasted by DJ Penelope (Cleopatra Coleman).
Sara Johnson, a promising dancer in high school, hopes to be admitted to study at Juilliard School and invites her mother to attend the audition. She fails the audition and soon thereafter learns that her mother has been involved in a fatal car accident in her haste to get to the audition.
Jim Street (Colin Farrell), a former U.S. Navy SEAL and hot-shot cop from the Los Angeles Police Department and his SWAT team are sent to stop a gang of robbers who have taken over a bank. His high-tempered partner and close friend Brian Gamble (Jeremy Renner) disobeys an order to not fire on the bank robbers, and accidentally wounds a hostage in the process. Gamble and Street are demoted by Captain Fuller (Larry Poindexter), the commander of the LAPD Metropolitan Division. Gamble quits following the argument with Fuller, and Street is taken off the team and sent to work in the "gun cage", where he looks after the gear and weaponry. Six months after the incident, the chief of police calls on Sergeant Daniel "Hondo" Harrelson (Samuel L. Jackson) to help re-organize the SWAT division. Hondo puts together a diverse team, including himself, Street, Christina Sánchez (Michelle Rodriguez), Deacon Kaye (LL Cool J), TJ McCabe (Josh Charles), and Michael Boxer (Brian Van Holt). The team members train together, eventually forging bonds of friendship. As a result, their first mission to subdue an unstable gunman is a success.
Following a party, brothers Mac (Damaine Radcliff) and Skinny Carter (De'Shawn Washington), with their friend Tyler Gage (Channing Tatum), break into the Maryland School of Arts and trash the school's theatre, damaging many of the props. When a security guard appears, Tyler helps the two escape, accepting full blame for the vandalism himself. He is sentenced to 200 hours of community service, which is to be served at the school. While working, he peers in on a dance class and meets Nora Clark (Jenna Dewan Tatum), a student preparing for her "senior showcase", an audition performance which could determine whether or not she is offered a job within any one of the professional dance companies to attend the performance. When Mac and Skinny pay Tyler a visit on the school's lot, Nora curiously watches from a window as Tyler dances with his friends, mockingly incorporating a mashup of break-dance and the ballet moves he has recently observed. When Nora's dance partner, Andrew (Tim Lacatena), sprains an ankle, Nora finds herself unexpectedly without a partner for her routine. Auditioning some sophomore students to replace him, she decides that none meet her expectations. Tyler offers to help, but Nora refuses. After demonstrating that he can handle the routine however, Nora reconsiders and convinces Director Gordon (Rachel Griffiths) to allow Tyler to rehearse with her. During their initial practice session, Tyler is antagonistic towards Nora as well as her boyfriend, Brett (Josh Henderson), both of whom respond with haughty attitudes. As they continue to rehearse, Nora and Tyler grow closer, each teaching the other about their respective styles of dance. Tyler also befriends a musician at the school named Miles (Mario), who has a crush on Nora's friend, Lucy (Drew Sidora).
The film follows a day in the life of Los Angeles Police Department officer, Jake Hoyt, who is scheduled to be evaluated by Detective Alonzo Harris, a highly decorated LAPD narcotics officer. In Alonzo's car, the officer sees teenage Mara Salvatrucha gang members dealing drugs in a park. Alonzo confiscates the drugs and tells Jake to take a hit of the marijuana. Jake refuses, but Alonzo puts a gun to his head and says that Jake's failure to use drugs could get him killed by a street dealer.
The seemingly random murder of their adoptive mother, Evelyn Mercer (Fionnula Flanagan), at a Highland Park, Michigan convenience store, brings four brothers back home to Detroit, Michigan to find out what happened. Originally under the impression the crime was a simple robbery-gone-wrong, the brothers soon discover that the robbery was merely a cover for what was, in fact, a hit put out on Evelyn. After this revelation, Bobby (Mark Wahlberg), Angel (Tyrese Gibson), Jeremiah (André Benjamin) and Jack Mercer (Garrett Hedlund) track down the hired guns who killed Evelyn. Refusing to say anything, they are unceremoniously executed by Bobby and Angel.
Sean (Ryan Guzman) and his crew the Mob from the previous film are in Los Angeles trying to make a living from dancing, but are turned down at every audition. After being refused at another audition, the Mob visit a club where they are noticed and challenged to a dance battle by another crew, the Grim Knights. The Grim Knights win the battle and the Mob decides to pack up and leave Los Angeles and return to Miami, thinking there is nothing left for them and that they aren't ready for Los Angeles.