"The Shadow Line" is a British crime detective series about the rivalry between the police and the mafia. Both sides are trying to achieve the same goal, but in different ways. In the city, the largest drug baron, Harvey Rattan, is killed. The state investigates his death through the experienced detective Gabriel, who suffers from partial amnesia after being injured on the job. On the other side, the "entourage" of the deceased - criminals and drug dealers - are also involved in the case. The outcome will determine the new power on the city streets.