Hanson, Hoffs and Ioki try to discover who is making synthetic heroin and experimenting on people with it. Also, Ioki tries to help a Chinese student deal with a spy trying to bring him home, and Hoffs fends off an unwanted suitor.
Hoffs and Ioki go undercover at a university whose disabled students are being raped. Officer Scanlon, one of Fuller's previous officers who was disabled after being shot, works with Penhall on the same case.
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.
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.
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.
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.
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.
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.
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.
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.