Glenn Close has come and gone. Forest Whitaker has come and gone. But this season – the last in this quite extraordinary series – has no need of guest stars to make it special. Vic Mackey, surely the most corrupt cop ever to take the lead in a TV show (murder of a fellow officer, abduction, torture, robbery, drug kingpin...) is about to get his comeuppance. And the end, when it comes, is not far off rivalling The Sopranos for sheer gob-smacking brilliance.