4x19 - Cold Squad

Cold Squad is convinced they have the necessary ammo to bring down killer Dean Bulmer, and Nicco goes so far as to promise the family of one of his unlucky victims that it's in the bag, but when a body found proves to belong to the man Bulmer is on trial for killing, the Squad realises that Bulmer has been fingered for the wrong murder, and it comes down to the moral question of whether to lie to keep a vicious killer in prison, or to tell the truth and have him set free.