When the Gun Goes Bang, Bang, Bang

The entire homicide division is present at a warehouse, when an undercover homicide cop was shot and killed. Upon arrival back at headquarters, Rizzoli interviews a witness to the murder, but things go awry when the drug dealers responsible storm headquarters at gunpoint and shoot the on-duty cop working the desk. Whilst everyone at the crime scene remains none the wiser, a desperate Rizzoli and Isles try to save Frankie's life, when it hangs in the balance on Maura's table after he is also shot by the assassins. The day takes an even darker turn when Rizzoli is held at gunpoint by the man responsible, the last person anyone ever suspected. In order to catch him, she makes the ultimate sacrifice.