A loud argument takes place inside a shabby house. A man with a bandanna tied around his head comes out, shouting, "I hate you! Nobody messes with me!" Doug and Harry, staking out the street in a car, witness this. Doug is irritated that the lead Harry's snitch gave them is bogus.
Doug gets a cell phone call and looks worried when he hangs up. Clavo cut himself and Doug wants to go straight to the hospital. Harry says they can't because they're on duty; he's sure Clavo will be fine. Harry does relent. Doug calls for backup to take over and tells Harry to get out of the car. Doug leaves. Harry watches as Bandanna Man is dropped off at the house. Bandanna Man knocks on the door with a gun in hand. He shoots the man who answers the door. A second man appears and shoots Bandanna Man. Men shoot at the getaway car. Harry doesn't do anything.
Doug sees a groaning Bandanna Man brought into the ER by paramedics; he's been shot in the back. A nurse brings Clavo to Doug. The little boy's forearm is wrapped in bandages. Doug picks Clavo up and hugs him. Harry arrives with Fuller in tow. "You're in a lot of trouble, Doug," the captain says softly.
Doug, in his uniform, is told by Internal Affairs that he's hereby removed from Jump Street. He's lucky not to be suspended for leaving Harry in the lurch like that. It doesn't matter that Doug had a family crisis; you can't leave your partner. Doug is reassigned to the 43rd Precinct. Harry goes into the Internal Affairs office next. Doug pretends not to see him.
In the 43rd Precinct locker room, we learn that Doug isn't the only new face. The precinct is getting a rookie named Dean Garrett. Doug is greeted by his fellow officers telling him that the 43rd is the "city's dumping grounds for washouts and rejects." An officer named Wolf howls, welcoming Doug to the pack.
Doug, on patrol with his new partner Wolf, is told, "We lost the war on drugs 10 years before they coined the phrase." They sit down for lunch at a Chinese restaurant. Wolf says junkies win the fight against a cop 9 times out of 10. Wolf opines that justice isn't up to cops; it's up to the courts who can't lock anyone up because the jails are overcrowded. Doug goes to the counter to pay his bill. The restaurant owner tells him police officers eat free.
Outside, Wolf asks if Doug has a problem with getting free food. He assures him that nobody in Chinatown would turn them in to Internal Affairs. They pull over a guy for running a red light even though two other people ran the same one. The driver offers to buy Wolf's pen to get out of the ticket, which is dumb even for this show. Wolf takes the $20, hands over the pen, and doesn't write a ticket.
Back in the police car, Wolf tells Doug it's Christmas every day at the 4-3. Doug isn't comfortable with the way things are done. Wolf informs him, "This is the real world. You gotta use it or it'll use you." He offers to let Doug join the Wolf Pack for a late-night run of some sort.
In a dark alley, the cops of the 43rd discuss the new rookie they're getting. Dean graduated the police academy in spite of bombing the final exam. He's also coming off a 6-week leave of absence for "family reasons." They wonder who the rookie knows to get that kind of time off. There's concern he could be a plant from Internal Affairs.
The cops kick in the door of a stash house. While Doug handcuffs a suspect, Wolf and another cop pocket some drugs. They find a bag of money under a floorboard and start flushing drugs down the toilet. Doug asks why they're flushing evidence. Wolf says they have to let their suspect go because there's no evidence. Outside, the cops split the stolen money. Doug refuses to take it at first but eventually gives in.
In the locker room the next morning, Doug and Wolf think somebody should keep an eye on rookie Dean in case he's IAB. Doug is elected to do until Wolf's friend, a police union rep, can tell them if Dean is who he appears to be. Dean, an eager-looking kid, is waiting for the other officers in the roll call room. The others give him a hard time, asking why he became a cop. He also tells him the desks at the back of the roll call room are off-limits to rookies.
When the officers remove their caps during roll call, everyone except Dean has a black streak across their forehead, most likely from grease paint or the like. In front of the sergeant, one of the senior cops threatens to make Dean his bitch.
On patrol, Doug learns that Dean is from New Jersey and worked for a ticket scalper at the Meadowlands as a kid. He reminisces about seeing some great games from the upper deck. You'd think a scalper could get his employee better seats. Dean asks Doug why everyone at roll call was "acting like I whacked your mothers or something." Doug again wonders how a rookie got 6 weeks off after the academy. Dean says he had "things to take care of."
A shifty-looking guy dumps what looks like a bag of trash in alley when he sees the cops. Doug and Dean sift through the bags, trying to find what the guy ditched. If this were Law & Order or NYPD Blue, this would be when they found a bag of body parts or something equally horrible. Dean gets a look inside one bag, almost throws up, and runs out of the alley. Doug checks the bag too.
Dean catches up to Mr. Shifty and arrests him. Mr. Shifty offers Dean money: "Come on, pig! It wasn't even my baby!" Disgusting!
Later, Doug, an unnamed black cop, Wolf, and Dean respond to a burglar alarm at a Chinatown store. The register drawer is open, but nothing else looks out of place. Doug tells Wolf about Dean arresting a guy for "disposing of a stillborn that died from its mother's habit." Wolf makes a highly inappropriate joke about Dumpster diving.
The store owner, Mr. Li, arrives. Wolf suggests that Mr. Li pay him $100 a week to have someone watch the store. Outside, Dean sees the junkie he arrested wandering the streets. "Son of a bitch," he complains, sounding a lot like another famous Dean, "I just arrested that guy this morning." Wolf basically tells him "them's the breaks."
At roll call the next day, the officers learn that one of their own was shot in another precinct. The suspect was arrested without incident. One officer pipes up that if he ever gets shot, he wants his partner to put his shooter in a coroner's van, not a squad car. People clap and cheer this proclamation. The sergeant doesn't say a word about the outburst, just dismisses everyone. Wolf tells Doug the Wolf Pack is meeting that night at Mr. Li's store. Doug should ditch his partner so they can all "split the dead presidents."
At lunchtime, Doug leaves Dean at the Chinese restaurant with instructions to order for everyone. Wolf takes Doug into a store to teach him "how to collect." In the restaurant, the owner looks suspiciously at the rookie cop sitting by himself with several plates of untouched food on the table. Dean puts on his coat, apologizes to the owner for the others not showing up, and asks how much the bill is. "No pay for police," the owner says again. Dean tells her he's not allowed to accept favors, goes back to the table, and sets down a wad of money.
In the store, Doug rings the counter bell for service and Harry steps out of the back room. Harry lies that Mr. Li is at the wholesaler's and he's filling in. He produces an envelope of money from the register and hands it over.
At Casa de Penhall, Judy tells Clavo the story of Pinocchio and kisses him good night. Doug wishes he had a bigger apartment so Clavo could have his own room. Out of Clavo's earshot, Doug confesses to Judy that he's afraid that he'll get killed before Clavo grows up. Judy has learned Harry is at Mr. Li's store investigating corruption at the 43rd.
Harry tells Cap'n Rufus he wants off the corruption case. Rufus can't do that; good undercover officers are hard to find. Besides, dirty cops give up the right to be called cops; they're just as bad as, if not worse than, regular criminals.
Doug and Dean catch some men playing craps on an apartment building roof. They all run, leaving their cash behind. Dean crumples up the money and tosses it off the roof. He's upset about Doug ditching him the day before; he can't understand why nobody trusts him. Doug tells Dean that if anything happens to him, Dean should worry about calling an ambulance before chasing the suspect. Doug has a nephew to take care of.
In the car, Dean notices something suspicious happening in a nearby parking lot. Doug tells him to call for backup and cover him. One of the suspicious guys hits Doug with a tire iron. Dean fires a warning shot in the air, then the men scatter. He chases the one who hit Doug into the street. Dean tackles the guy, but only manages to get one cuff one. The guy starts punching Dean as backup arrives to pull him off.
Doug assures one of the other cops that he's okay. Wolf shoves Dean against the side of the car, yelling that he should've waited for backup before chasing the guy. Wolf calls Dean a snitch and starts patting him down, threatening, "If you're wired, you're dead!" Dean struggles. His uniform shirt is ripped open, revealing nothing but a Kevlar vest underneath.
After work, Doug tucks Clavo in and examines the nasty bruise on his forearm. He probably oughta get that looked at; stress fractures can sneak up on you. I lived with one for a week without noticing it. Doug unbuttons his uniform shirt. There's a microphone taped to his vest. He takes the recorder off his belt, rewinds the tape, and listens to Wolf's death threat.
Two unnamed cops from the 43rd go to shake down Harry again. One partner finds baggies of drugs on the desk in the back room; there are also bricks of money in an appliance box. Harry pays them off and they leave. In the locker room later, the unnamed cops tell Wolf what they found at Mr. Li's store. They want to knock the place over. Wolf found out that Dean isn't Internal Affairs; he got 6 weeks off due to family problems. They take a vote and agree to let Dean into the Wolf Pack.
Late that night, someone knocks on Doug's door. It's Dean. Doug steps into the hall to talk because Clavo is asleep. Dean is disappointed that Doug turned out to be dirty. He looked up to Doug. Dean tells a story about why he became a cop. In 7th grade, Keith, a bully, was beating him up pretty badly on a sidewalk when a police car pulled up. The cops pulled Keith off Dean and drove Dean home. Dean's sorry he believed in the "childish ideal" of protecting and serving for so long. Doug tells him not to quit believing in that.
Doug has a sit-down with Internal Affairs and tells them about the planned hit on the appliance store. After the bust, Doug will be reinstated to Jump Street. Doug doesn't want to be there when the robbery happens because he's afraid Dean will do the wrong thing and get swept up with the rest of the Wolf Pack. The Internal Affairs guy agrees to work around Doug.
We see the Internal Affairs guy giving a chalk talk in the roll call room about the plan to hit Mr. Li's appliance store. Their team will move in after "the transaction" takes place. The Wolf Pack will be at a Chinese restaurant, which Doug will leave after he gets a phone call about a fake family emergency.
At the restaurant, Dean agrees to be part of the plan because he thinks Doug is still part of it. One of the Wolf Pack will have to keep their gun out in case the "Oriental dealers" freak out and not hesitate to shoot. Doug volunteers to do that part. The restaurant owner brings him the phone. Doug answers and pretends it's a routine call from his babysitter. He leaves with the rest of the Wolf Pack.
The Wolf Pack descends on Li's Appliances. Doug holds his gun on Harry. Wolf tells Harry they're teaching him a lesson about running drugs in their precinct. Dean draws his own gun and says, "Okay, Doug, put the gun down." Doug hisses that he's IAB. The rest of the Wolf Pack emerges from the back of the store with loot. Dean tells them they're all under arrest. One of the unnamed cops tries to shoot the rookie. The SWAT team rushes in, followed by Internal Affairs.
The head Internal Affairs guy tells them not to arrest Doug. A pair of cops grabs Dean. Doug assures them the kid is clean. Harry, Dean, and Doug watch the dirty cops being lined up against the counter.
The next time Dean comes to work, someone has spray-painted the word RAT on his locker. Someone has spray-painted SNITCH on Doug's. "I wonder if this ever happened to the cop who saved me from Keith Sharpelli," sighs Dean. He thinks it sucks that IAB kept Doug in the dark like they did.
Doug shows Dean the Chapel. "It's no Saint Patrick's," says Dean. Doug tells him of course not; Saint Patrick's is a cathedral and this is a chapel. Dean doesn't want his first day at the Chapel to be like his first day at the 43rd. "Welcome to Jump Street," Doug says in the squadroom. End of episode and Season 4. It should be interesting to see what role Dean plays in the 5th and final season.