In a season-long subplot, the Barksdale organization continues its drug trafficking despite Avon's imprisonment, with Stringer Bell assuming greater power. McNulty harbors a grudge against his former commanders for reassigning him to the marine unit. When thirteen unidentified young women are found dead in a container at the docks, McNulty successfully makes a spiteful effort to place the murders within the jurisdiction of his former commander. Meanwhile, police Major Stan Valchek gets into a feud with Polish-American Frank Sobotka, a leader of the International Brotherhood of Stevedores, a fictional dockers' union, over competing donations to their old neighborhood church. Valchek demands a detail to investigate Sobotka. Cedric Daniels is interviewed, having been praised by Prez, Major Valchek's son-in-law, and also because of his work on the Barksdale case. He is eventually selected to lead the detail assigned just to investigate Sobotka; when the investigation is concluded Daniels is assured he will move up to head a special case unit with personnel of his choosing. Life for the blue-collar men of the port is increasingly hard and work is scarce. As union leader, Sobotka has taken it on himself to reinvigorate the port by lobbying politicians to support much-needed infrastructure improvement initiatives. Lacking the funds needed for this kind of influence, Sobotka has become involved with a smuggling ring. Around him, his son and nephew also turn to crime, as they have few other opportunities to earn money. It becomes clear to the Sobotka detail that the dead girls are related to their investigation, as they were in a container that was supposed to be smuggled through the port. They again use wiretaps to infiltrate the crime ring and slowly work their way up the chain towards The Greek, the mysterious man in charge. But Valchek, upset that their focus has moved beyond Sobotka, gets the FBI involved. The Greek has a mole inside the FBI and starts severing his ties to Baltimore when he learns about the investigation. After a dispute over stolen goods turns violent, Sobotka's wayward son Ziggy is charged with the murder of one of the Greek's underlings. Sobotka himself is arrested for smuggling; he agrees to work with the detail to help his son, finally seeing his actions as a mistake. The Greek learns about this through his mole inside the FBI and has Sobotka killed. The investigation ends with the fourteen homicides solved but the perpetrator already dead.