Baltimore Det. Jimmy McNulty finds himself in hot water with his superior Major William Rawls after a drug dealer, D'Angelo Barksdale who is charged with three murders, is acquitted. McNulty knows the judge in question and although it's not his case, he's called into chambers to explain what happened. Obviously key witnesses recanted their police statements on the stand but McNulty doesn't underplay Barksdale's role in at least 7 other murders. When the judge's raises his concerns at the senior levels of the police department, they have a new investigation on their hands. Lt. Cedric Daniels is put in charge with Kima Greggs as the lead detective. As for Barksdale, he finds himself demoted to a low-level dealer after his arrest and he obviously has to prove himself yet again.

After two weeks on the job, the team still doesn't have a photo of their principal target, Avon Barksdale. Freamon has a solution when he hears Avon was a Gold Gloves boxer. In the aftermath of the near riot at the towers, Lt. Daniels stands by his men even though he thinks they were stupid to do what they did. He's ordered to lead a raid on the low-rise units in the projects but McNulty rebels and refuses to participate in a raid that's just being put up for show. Dissatisfied with the antiquated equipment they have to work with, McNulty asks his friend at the FBI to lend them listening devices. His friend also has some information for him about Lt. Daniels. D'Angelo isn't around when a gang led by someone called Omar robs his stash.

Due to the camera at Orlando's, the detail gather enough information to arrest Avon and many of his people, but, with Wallace dead, they are unable to bring charges against Stringer, who's left on the street. However, disgusted that Avon and Stringer had Wallace killed, D'Angelo flips on the entire organization, giving the detail more information than they could have ever hoped for. As Daniels figures out who the snitch is in the unit, Herc is shocked when he is passed over for promotion in favor of Carver, who scored lower on the sergeant's exam. In Philadelphia, Wee-Bey is arrested and gladly admits to murder after murder. Finally figuring out why Avon has been buying vacant properties in the city, Daniels, McNulty, Freamon and Pearlman take their evidence of political involvement to the FBI. Meanwhile, D'Angelo's mother, Brianna (Michael Hyatt), attempts to convince him to stand with the family.

Bodie's disastrous sales efforts result in a tongue lashing from Stringer Bell. Ziggy pulls Johnny Fifty into a new caper that makes the Greeks pay big money. McNulty goes undercover in a brothel. As Valchek fumes over the change of targets and Burrell pulls the rug from beneath him, Daniels and Pearlman maintain their composure.

The detail uses satellite technology to its advantage. Bodie is unhappy that Proposition Joe's people are selling on his turf. Valchek visits the FBI in an attempt to get real results on the docks. Ziggy's deal with Double-G goes bad in a big way. Greggs considers motherhood and Prez makes a major blunder.

The detail makes a desperate move. Nick's deceit is in the open, as Sobotka is overwhelmed by bad news. The Greeks confidently ease out of a brief encounter with the detail and Omar's suspicions are validated. The detail hopes to find Vonda's boss. Nick hopes to repair relations with the Greeks and Sobotka is forced to make a difficult choice.

The detail has a setback. Russell and Bunk revisit Philly, looking for evidence. Brother Mouzone talks with Stringer Bell regarding their agreement, leaving Bell to contend with Avon Barksdale. McNulty and Greggs return to the Westside, where they discover new connections. Herc and Carver feel disrespected by fellow officers. Nick tries to come to terms with the Greeks, and himself.

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. Colvin sees the benefits of his plan working. Carcetti confronts a hurdle he must clear if he wants to run for higher office, while Marlo appears to take the bait set by the Barksdale crew.

Responding to an officer's call for help, McNulty and Prez turn up the wrong alley with unanticipated results. Cutty is surprised to find help from within Baltimore's power structure for his proposed boxing gym. Omar decides to go it alone against Avon Barksdale and Stringer Bell. Bubbles is wired up and sent into Hamsterdam

The wire begins to yield information about the Barksdale organization. Stringer and Avon reminisce on how far they have come. McNulty finds the way to a key piece of the puzzle in an unlikely place. Awaiting his fate, Colvin works behind the scenes to shape the outcome of Amsterdam, while protecting his men from possible repercussions. Bubbles considers a new partner.

Although he tells Sydnor the Davis investigation could be a 'career case,' Freamon keeps a wary eye out for Marlo, who takes care of some unfinished business and strikes a business deal with Barksdale.

Baltimore's renewed police commitment brings fresh recruits to Daniels and McNulty, starting with Carver. Facing a new political challenge, Carcetti is forced to make dangerous political deals.

Carcetti maps out a damage-control scenario with the police brass in the wake of a startling revelation from Pearlman and Daniels. Their choice: clean up the mess...or hide the dirt.