It's very good. Mirren's Jane Tennison, now a Detective Superintendent at the London Metropolitan Police, has to appease her superiors, handle her subordinates, say something to the press, establish rapport with witnesses, think the investigation (the tortured body of a Bosnian Muslim immigrant has been found, presumably killed by a Serbian immigrant) through, and somehow have a private life of her own along the way. I don't see that level of realism in cop shows nowadays, not even the better regarded ones.
Maybe one of the most disturbing moments was an autopsy report, where the coroner casually reports deep tissue damage under the murder victim's flesh, where she had been burnt by cigarettes; she had been burnt years before. This is the one detail that throws Mirren's otherwise hardened Tennison: the old and new burn patterns match, burn for burn, implying that she had been killed by the same man who had tortured her when she was ten.
Not the kind of detail Gibson's capable of putting onscreen, is it?