The Wire - Season 1

The first season introduces two major groups of characters: the Baltimore police department and a drug dealing organization run by the Barksdale family. The season follows the investigation of the latter over its 13 episodes.
An investigation into a large Baltimore based drug dealing is triggered when detective Jimmy McNulty meets privately with judge Daniel Phelan following the acquittal of D'Angelo Barksdale for murder after a key witness changes her story. McNulty tells Phelan that the witness has probably been intimidated by members of a drug trafficking empire run by D'Angelo's uncle, Avon Barksdale, having recognized several faces at the trial, notably Avon's second-in-command, Stringer Bell. He also tells Phelan that nobody is investigating Barksdale's criminal activity, which includes a significant portion of the city's drug trade and several unsolved homicides.
Phelan takes issue with this and complains to senior Police Department figures, embarrassing them into creating a detail dedicated to investigating Barksdale. However, owing to the department's dysfunctionality, the investigation is intended as a façade to appease the judge. An interdepartmental struggle between the more motivated officers on the detail and their superiors spans the whole season, with interference by the higher-ups often threatening to ruin the investigation. The detail's commander, Cedric Daniels, acts as mediator between the two opposing groups of police.
Meanwhile, the organized and cautious Barksdale gang is explored through characters at various levels within it. The organization is antagonized by a stick-up crew led by Omar Little, and the feud leads to several deaths. Throughout, D'Angelo struggles with his conscience over his life of crime and the people it affects.
The police have little success with street-level arrests or with securing informants beyond Wallace, a young low-level dealer and friend of D'Angelo. Eventually the investigation takes the direction of electronic surveillance, with wiretaps and pager clones to infiltrate the security measures taken by the Barksdale organization. This leads the investigation to areas the commanding officers had hoped to avoid, including political contributions. When an associate of Avon Barksdale's is arrested by State Police and offers to cooperate, the commanding officers order the detail to undertake a sting operation to wrap up the case. Detective Kima Greggs is seriously hurt in the operation, triggering an overzealous response from the rest of the department. This causes the detail's targets to suspect that they are under investigation.
Wallace is murdered by his childhood friends Bodie and Poot, on orders from Stringer Bell, after leaving his "secure" placement with relatives and returning to Baltimore. D'Angelo Barksdale is eventually arrested with a large quantity of drugs, and learning of Wallace's murder, is ready to turn in his uncle and Stringer. However, D'Angelo's mother convinces him to rescind the deal and take the charges for his family. The detail manages to arrest Avon on a minor charge and gets one of his soldiers, Wee-Bey, to confess to most of the murders, some of which he did not commit. Stringer escapes prosecution and is left running the Barksdale empire. For the officers, the consequences of antagonizing their superiors are severe, with Daniels passed over for promotion and McNulty assigned out of homicide.