A ruthless and cunning young player, Marlo Stanfield caught everyone off guard with his insurgent campaign against the larger Barksdale crew. Although Stringer Bell was inclined to grant generous terms to the upstart, Avon Barksdale eventually returned from prison and was disgusted to learn that a young, spirited gangster had run his boys off some prime real estate. Belatedly attempting diplomacy to avoid the violence and police attention that would result from a drug war, Bell offered membership in Prop Joe's New Day Coop and the expertise of older heads in money laundering to the younger deal. Marlo rejected any alliance however and as the war escalated, it became clear that he was very much like Bell's partner in outlook.
Gangsters at heart, Avon wanted his corners and Marlo wanted Avon's crown. Even as Avon was forced to give up Bell to appease Brother Mouzone, he began to see that he had both underestimated the costs of war and Marlo as well, and that the territory in question was in no way worth the price. But the war ended abruptly with the police raid on Barksdale's safehouse. At his arraignment in a city circuit court, Avon looks back to see his younger rival taking a seat in the spectator's gallery. Avon mouths "Marlo?" and the younger dealer confirms with a nod. Avon nods his acknowledgement and the crown is passed. Taking control of West Baltimore, Marlo goes head to head with Omar, and eventually joins the New Day Co-op to get an inside look at how they work. Meanwhile, Marlo's crew hides the bodies of those that got in the way in vacant buildings. This works until Lester Freamon uncovers the secret tombs, and Major Crimes is able to turn their attention to Marlo once again.