McNulty continues to defy his bosses in his pursuit of Stringer. Colvin's outlandish new rules on dealing drugs hit the streets.
Stringer breaks a fundamental rule of the game, prompting Omar to vow to end the feud once and for all. Meanwhile, Prez makes a fatal mistake.
Avon readies his troops for a war against Marlo. Meanwhile, as the crew works towards the upper levels of the Barksdale organisation, McNulty has doubts about the path he's chosen for himself.
Colvin faces tough questions over the sharp drop in crime in his district. Meanwhile, Stringer shocks Avon with a startling confession.
While Avon and Stringer disagree on how to handle Marlo, Cutty considers his future after facing the realities of gangster life.