This crime-drama follows a single sprawling drug and murder investigation - one that culminates in a complex series of dangerous wiretaps and surveillance.
Baltimore homicide detective Jimmy McNulty gets into hot water and winds up assigned to a detail of narcotics outcasts investigating drug lord Avon Barksdale. Meanwhile, Avon's nephew D'Angelo, fresh off beating a murder rap, is demoted upon his return to the gang.
McNulty feels the heat when a witness who testified against D'Angelo is found murdered. Meanwhile, Greggs is given the lay of the land regarding Avon Barksdale's key players, and Herc, Carver and Prez find big-time trouble at the towers.
The early-morning 'field interviews' by Herc, Carver and Prez result in a minor riot, a boy losing an eye, and some bad publicity for the department. On the other side of the law, D'Angelo teaches Wallace and Bodie how to play the game... of chess.
Greggs and McNulty try to get Hardcase to turn informant as those caught in the raid are charged. Meanwhile, McNulty takes Bubbles on a cultural field trip, Herc and Carver try to track down Bodie, and Barksdale places a bounty on the head of rival gang leader Omar.
McNulty's detail finally gets 'clone' pagers to track Barksdale and his gang, but nobody can crack the codes used by the callers. Meanwhile, Bell instructs D'Angelo on how to school his lookouts while simultaneously flushing out a possible snitch.
When Rawls looks to make a premature arrest for three murders that are linked to D'Angelo and Barksdale, McNulty and Greggs argue for a delay in order to preserve the valuable wiretap gains they have made. Meanwhile, Wallace and D'Angelo struggle with their consciences.
Tipped off by the wire, Greggs, Herc, Carver and Freamon make a bust, but the incident makes Avon and Stringer suspicious, leading them to close shop in the pit. Meanwhile, Bunk and McNulty look for another witness in the Gant slaying and hunt a new suspect.
An unlikely source gives McNulty the tag of a car driven by Stringer Bell. Meanwhile, Greggs and Carver bust a congressional aide carrying dirty cash but are forced to let him go. Later, Omar justifies his reputation as a 'loose cannon'.
Barksdale plays an expensive game of one-upmanship with an east-side rival. Meanwhile, Herc and Carver take some cash off of Wee-Bey's hands, and Omar resurfaces with a bang.
With Wallace in custody, McNulty and Daniels try to figure out what to do with him in the months before he testifies. Meanwhile, Sydnor and Carver track down one of Barksdale's stash houses, and Prez shows off his 'gift for the paper trail'.
The police turn up the heat on tracking down Savino, Wee-Bey and Little Man. Meanwhile, Burrell orders Daniels to hit drug dealers for results that will impress the press; Barksdale sees his ranks thinning after the hit on Orlando, and Bubbles tries to stay sober.
The low-rise pay phones are out of service so McNulty and Daniels try to keep pace by tapping Barksdale's office. Meanwhile, Bodie gets some new responsibilities from Stringer, Freamon gives Shardene a 'new look', and D'Angelo goes to NYC on an errand for his uncle.
It transpires that every crew has weak links… including Avon Barksdale's. With the heat turned up in the high-rises, Daniels and McNulty turn to a higher authority in an effort to crack the case wide open.
A wave of urban reform brings down the notorious Franklin Terrace public housing towers, forcing the Barksdale drug crew to find a new home on the streets of West Baltimore.
Omar continues his strikes on Barksdale stash houses, while Bodie faces a critical test against Marlo. Elsewhere, as the wire on Proposition Joe continues to yield little, a restless McNulty launches his own reinvestigation into the suicide of D'Angelo Barksdale.
Colvin feels the sting of Burrell and Rawls during a Comstat assessment of his district's felony numbers. Meanwhile, a blown wiretap forces Daniels' detail to turn to a new target, and Proposition Joe warns Stringer Bell that the police have been tapping phones.
West Baltimore residents get some straight talk at a community meeting from Major Colvin. Elsewhere, Bubbles finds gainful employment, Stringer lunches uptown, and Bunk dangles the promise of immunity to a group of corner boys... in exchange for some help.
Frustrated in his reform efforts, Colvin arms himself with intelligence and delivers a message to the next level of corner management. Meanwhile, McNulty sees Stringer Bell's legitimate business dealings as a sign that he is now unreachable as a drug target.
Stringer Bell gets a lesson in construction management while Bunk uses shoe-leather to catch up with Omar and deliver a message. Elsewhere, Colvin unleashes the troops on the corner boys, and Avon sends Cutty and Slim Charles up against Marlo.
Stringer Bell learns from Donette that she's told Brianna about McNulty's visit and that Brianna is likely to talk to him. Meanwhile, Daniels blows up over the real reason The Detail was reassigned to the Western District, and Herc discovers a blast from the past.
With Amsterdam running full-tilt, Carver and Truck discover there really is no honour among thieves. Elsewhere, Prez impresses the detail with what he's found out from Bodie's cell phone - information that sends McNulty and Greggs on a road trip.
Responding to an officer's call for help, McNulty and Prez turn down the wrong alley, with unanticipated results. Meanwhile, under orders, a Barksdale crew violates the unspoken Sunday truce with gunplay, increasing discontent among the New Day Co-op members.
Brother Mouzone returns to Baltimore on a mission of revenge and casts a wide net in his search for Omar, who has his own plan for vengeance. Elsewhere, Colvin puts off a reporter inquiring about Amsterdam, whilst Burrell delivers news to City Hall.
The wire begins to yield information about the Barksdale organisation, though finding links to the top proves elusive. Meanwhile, Stringer and Avon reminisce about how far they've come, with each harbouring plans for the future.
A reticent Avon readies his troops for a seemingly endless war against Marlo. Meanwhile, as the detail works towards the top rungs of the Barksdale organisation, McNulty reassesses his pursuit of Stringer Bell.
Whilst McNulty and The Detail continue staking out Marlo's crew, Sergeant Carver faces a cauldron of discontent from officers coping with unpaid overtime. Meanwhile, though he wants to keep his promise to lower crime, Mayor Carcetti is strapped by his pledge to schools.
Although he tells Sydnor the Davis investigation could be a 'career case', Freamon keeps a wary eye out for Marlo, who strikes a business deal with Barksdale. Meanwhile, Carcetti throws the police a bone by removing the cap on secondary employment.
Carcetti's master plan for the police is leaked to the press, sending the brass into a panic. Meanwhile, McNulty shares some inside info with Alma, but her subsequent story doesn't cause the splash either envisioned. Undaunted, McNulty looks for a new ally in Freamon.
The newspaper scramble to confirm surprising news from City Hall, but fear losing the scoop to TV media. Meanwhile, Proposition Joe pays his last respects to a fallen colleague, and prepares to make himself scarce in anticipation of a showdown.
Marlo forges an alliance with a drug connect who shows him a new communications trick. Meanwhile, McNulty's case is getting increased attention from the newspaper, thanks in large part to Templeton being added to the reporting team.
Mystified by Omar's disappearance, Marlo and Chris ramp up their efforts to locate their nemesis. Elsewhere, after attending a sparsely attended waterfront ceremony, Carcetti fires away at a larger press event and recasts himself as a champion for the homeless.
An unexpected call puts Templeton in the spotlight and gets McNulty more attention than he expected. Elsewhere, Omar sends Marlo a message, Carcetti proves he's still an adept fundraiser, Carver gift-wraps a witness for Bunk, and Bubbles shows a reporter the ropes.
Baltimore's renewed police commitment brings fresh recruits to Daniels and McNulty, starting with Carver. Meanwhile, as the Pulitzer season winds down, Haynes approaches Templeton about his sources, and Carcetti is forced to make some dangerous political deals.
With Steintorf ordering Rawls to initiate remedies for the rising crime rate, Freamon's vigilance pays off, sending Sydnor and the department into overdrive. Although Daniels is originally delighted, a further probe with Pearlman reveals some troubling information.
Carcetti maps out a damage-control scenario with the police in the wake of a revelation from Pearlman and Daniels. Meanwhile, with his leads drying up, McNulty asks Landsman to pull police off the homeless case - until a fresh homicide ramps up the investigation.
Four boys from West Baltimore, Michael, Namond, Randy and Dukie, play out their summer vacation in the streets. The boys are then stirred into action when Dukie is beaten up, leaving Randy to concoct a retaliation plan against the rival gang.
Herc's soft-duty job with the mayor takes an unexpectedly hard turn. Meanwhile, despite the potential damage to her career, Pearlman provides Freamon and Sydnor with subpoena ammunition for their 'grizzly bear' hunt in City Hall.
With his poll lead shrinking, Royce resorts to extreme measures to stall Carcetti's momentum. Meanwhile, Michael proves adept as a runner, alerting both Bodie and Marlo, and Rawls replaces Asher with 'company man' Charles Marimow, who pushes a new agenda on the detail.
With Freamon and Greggs moved to Homicide, Herc and Dozerman join Marimow in the stripped-down Major Crimes Unit. Meanwhile, Cutty gets a 'custodial' job at Tilghman School mopping up truants, but can't make any headway in his efforts to mentor Michael.
Valchek leaks details of the Braddock case to Carcetti, who contemplates how to best leak it to the press... with the ensuing negative attention turning Royce against Burrell. Meanwhile, at school, Prez's reward and punishment programme meets with mixed results.
With Election Day near, the three mayoral candidates make last-minute appeals, with Carcetti seeking votes as he responds to a potentially devastating smear. Elsewhere, whilst following through on a promising video lead, Herc finds out just how elusive Marlo can be.
With the election finally over, Royce and Carcetti make their peace and contemplate their respective futures. Meanwhile, Marlo looks to identify his pursuers, infuriating Herc, who begs Carver to help; and Omar, who has a bounty on his head, calls in a favour to Bunk.
To monitor the pulse on the street, Carcetti makes the rounds with members of the force. Elsewhere, Herc, who has Marimow on his case, decides to resort to strong-arm tactics to retrieve his stolen camera, but Marlo isn't impressed.
After being in prison, Poot returns to the corner and is welcomed back by Herc and Dozerman. Meanwhile, Carcetti engages in a battle with City Council President Campbell; rewards Daniels with a promotion; and hits a snag in his efforts to relieve Burrell of his duties.
Acting on Clay Davis' advice, Burrell seeks to burnish his reputation by ordering the department to double the number of street arrests. The mandate does not sit well with McNulty though, who instead sets his sights on cracking a string of church robberies.
After flexing his muscles around the city, Carcetti faces his first dilemma when a group of ministers protest Herc's mistreatment of one of their own. Meanwhile, Michael and the boys enact an elaborate revenge plot on a mean cop, and Namond takes a leap of faith.
On the trail of missing bodies, Freamon turns to a higher authority after being rebuked by Landsman. Elsewhere, Colvin approaches Deacon and Watkins to help keep his experimental class funded, and Bubbles considers taking extreme measures to rid himself of his nemesis.
The bodies from the vacants continue to pile up while Burrell offers his support to Daniels and forgives Rawls for crossing him. Elsewhere, Bubbles' revenge plan backfires, and Proposition Joe looks to the Co-op to pay shipment losses... but finds them uncooperative.
McNulty, reassigned to the marine unit, sticks City Homicide with the body he fishes out of the harbour. Nick negotiates a deal to steal a container from the docks but The Greeks end up reneging on the deal, leaving Russell to discover the bodies of 13 women in the aban
Rawls tries to pawn off the shipyard investigation to another jurisdiction after McNulty sends it his way. Valcheck goes after Sobotka and his union with a little help from above. Bunk, Freamon and Russell end up having to track a container ship to Philadelphia.
Bunk and Freamon chase their crime scene, a container ship, to Philly, where none of the crew finds it useful to speak English. Elsewhere, Lieutenant Cedric Daniels, disgusted with his exile to the evidence control unit, lets it be known he's going to leave.
Sobotka reprimands his nephew Nick for stealing the cameras and orders him to bring the cargo back before it's too late. Meanwhile, McNulty is on a self-assigned moral mission to identify his floater, but his old partner, Bunk, says they have a more pressing matter.
Ziggy loses his prized Camaro to drug dealers who aren't buying his alibis about not paying up. Meanwhile, unable to dump the homicide investigation on other police agencies, Colonel Rawls decides to lay the blame on Bunk if the cases go unsolved.
Trying to let go of work and return to his marriage, McNulty gives up on identifying his Jane Doe. Elsewhere, in their investigation of Sobotka, the detectives discover a pattern and explain the connection to Daniels, but he's still not convinced.
Sobotka gives his lobbyist abuse over the status of port legislation. Russell then tells Sobotka the investigation is over but a port computer is cloned and when a container goes missing, the detectives follow.
McNulty is back to his old self, on a drunken binge. Meanwhile, urged by fellow stevedores to fight Maui, Ziggy is again humiliated, but has a moment of redemption later at the bar. Elsewhere, Bunk is worried about McNulty so he asks Daniels and Rawls for their help.
Bodie's effort to improve sales ends disastrously, forcing Bell to rethink his strategy. Meanwhile, Ziggy pulls Johnny Fifty into a new caper that should have the Greeks paying off big, and McNulty, undercover and outnumbered, awaits 'rescue'.
Bodie is unhappy that Proposition Joe's people are slinging on his turf, but business flows until a new face from New York arrives... so Stringer Bell looks for an unlikely solution to the problem. Meanwhile, The Detail uses satellite technology to its advantage.
With the clock ticking, The Detail makes a desperate move and Daniels furiously rebukes Landsman for dropping the ball. Meanwhile, Nick's deceit is out in the open, and Sobotka is overwhelmed by bad news.
The Detail has a setback and needs a new co-operator, whilst Russell and Bunk visit Philly, looking for evidence. Elsewhere, Brother Mouzone talks with Stringer Bell regarding their agreement, leaving Bell to deal with Avon Barksdale.
