An ex-con who is mentored by Hoffs is suspected of reverting to his old ways of stealing cars. Although Hoffs has her doubts, McCann investigates.

Hoffs witnesses the drive-by-shooting of a gang member, and she goes undercover in her gang with dual objectives: to find her killer and to take down the leader of an associated gang, who is linked to a large gun-running ring.

A teacher is beaten to death by a group of extortionists after he starts a boxing club to help other students learn to defend themselves against them. Fuller, who is grieving the loss of a friend who died suddenly of a heart attack, goes in as the teacher's replacement, while Hoffs and McCann go in as students.

McCann goes undercover on a high school football team to investigate the death of a player, and he finds that a company has been dumping toxic waste at a site near the school.

Hoffs is sued for entrapment by a man who she busted for soliciting her while she was undercover as a prostitute. The case becomes personal when the man is represented by the ex-wife of the man Hoffs is dating.

McCann infiltrates a group of Satanists who have been attacking homeless people while Fuller goes undercover as a homeless man.

The Jump Street unit investigates a group of kids that has been robbing the homes of elderly people. Meanwhile, Fuller begins dating the mother of one of the suspects.

A pompous Fed comes to Jump Street and tells Fuller, they're trying to find some a way to have probable cause to search the home and warehouse of a man, they believe is smuggling in drugs. The Fed wants Fuller to send someone to get close to the man's daughter. Mac begrudgingly does it. But is uncomfortable using the girl like that. And his girlfriend comes to see him, to see if they pick up where they left off.

A news anchor criticizes the police on live TV when they show no results after searching for her missing daughter. The case is reassigned to McCann, who quickly finds the girl, but he also finds more than he bargained for when he discovers that both the girl and the mother are keeping secrets.

Joey kills someone in the line of duty. To help him cope, his psychologist recommends that he enter into an experimental program in which he helps care for a drug-addicted baby.

A woman who has been raped asks for Judy's help. When the Jump Street team looks into it they find that the accused man has an alibi and campus security has no record of the report, leading them to believe there has been a cover-up.

Hoffs witnesses two officers harass three black kids that she knows. She convinces the kids to testify against the officers, but the investigation is at risk of stalling when the officers try to scare them out of testifying.

Doug is shot and while comatose, he meets people he knows who are gone, like his wife, Marta. When he wakes up, he learns that Clavo has been keeping his distance, because he can't deal with losing someone he cares about. So Doug has to decide if he should continue being a cop.

When a student gets killed while trying to commit a robbery, Fuller sends the team to check it out. And the trail leads them to a place where students buy and sell school papers.

A star football player is killed when he is hit by a car. McCann goes undercover as his best friend's biology tutor to try to find the killer, but he is unsure of how to proceed once he develops feelings for the girl.

At special camp for Delinquent Children, one of the charges decides to bolt but dies in what appears to be an accident. However, Doug and Joey are sent there to see if the man in charge is too hard on them. While Judy and Mac check out the deceased.

Doug Penhall's estranged brother, Joey, transfers to the Jump Street Unit. After his attempts at making amends with Doug are rejected, he takes an assignment in which he must go deep undercover in a religious cult in order to extract a man's daughter and to prove that the cult is involved in illegal activities.

When there's an outbreak of Ecstasy in a high school, Hoffs and McCann are sent to investigate. And it seems the school has a zero tolerance and has all the students take drug tests. When Hoffs takes the test, she comes up positive and is pulled out and is grilled by I.A. Mac decides that the student who spearheads the anti-drug campaign at the school is a person of interest.

A narcotics officer goes undercover with the Jump Street crew to help bust a drug dealer. Penhall develops feelings for her, but problems arise when she is suspected of being addicted herself.

New Jump Street recruit Officer McCann is assigned to get close to a mentally handicapped youth in order to find out who murdered his partner in a buddy system which paired him and other mentally handicapped kids with troubled youths. Meanwhile, Hoffs and Penhall try to find out more about McCann's background.

As they attempt to adjust to the Jump Street program, Officers Rocky and Garrett go undercover in a high school to flush out its biggest drug dealer. While Garrett tries to have some fun with his new persona, Rocky fears that a teacher may be coming on to her. Meanwhile, Hoffs tries to buy her dream house.

Hoffs goes undercover inside a massage parlor that is also believed to be a brothel for underage girls, while Officer Garrett goes undercover as a patron. Meanwhile, a DEA agent is also investigating the owner of the parlor for drug trafficking.