Responding to an officer's call for help, McNulty and Prez turn down the wrong alley, with unanticipated results. Under orders, a Barksdale crew violates the long-standing, but unspoken, Sunday truce with gunplay, increasing discontent among the New Day Co-op members. Stymied by the bureaucracy in his effort to open a gym, Cutty is surprised to find help from within Baltimore's power structure. Omar decides to go it alone against Avon and Stringer Bell, who are pressed by Brianna for some answers. Bubbles is wired up and sent into Amsterdam to help make the case against the Barksdale organization, while Pearlman and Daniels confront a cell-phone company over its foot-dragging on wiretap orders. Proposition Joe goes to Vinson in an effort to broker peace between Marlo and Avon, while a murder in Amsterdam presents new challenges and further divides the Western District troops and their allegiance to Colvin. Councilman Gray tells Carcetti he's running for mayor and offers him the council president's slot on his ticket.