Episode 8

An Indian submarine strays into Pakistani waters, Pakistan seizes it, and two nuclear powers stand a finger's width from war. The Prime Minister brings both sides to London for talks, which is where the episode gets interesting, because there are people who need those talks to fail. The conspiracy finally wears its name out loud: Nightingale. And Sarah Caulfield is part of it.

A friendly Chinese diplomat tries to warn the attendees about an attack on the talks and is assassinated before he can pass the information on. MI5 is sure an incident is coming, designed to push India or Pakistan over the edge, and when the Indian delegation abandons the negotiations it looks as though the plan has worked. The talks were never really about talking, and everyone in the room knows it. Lucas and Ros put themselves in the middle of the hotel as a last throw, and the hour lets them stay there.

Ben Richards and David Wolstencroft wrote it, and Alrick Riley directed. Richard Armitage's Lucas and Hermione Norris's Ros carry the final gamble, with Peter Firth's Harry directing from the edge. Genevieve O'Reilly's Sarah Caulfield is the quiet shock of the season, Mark Aiken is Russell Price, Nicholas Khan is President Mudasser, Joshua Jo is Wu, Tobias Menzies is Andrew Lawrence, Shazad Latif is Tariq Masood, and Ben Peel is the MI5 Officer.

The hotel is a fine place for a showdown, and the show knows it, closing the season inside one. The horror it works with is people who would use a bomb, which is more honest than any countdown. Nuclear brinkmanship has rarely looked this domestic. The season has been building to this room, and the room delivers. It is the rare finale that feels like a promise of more, and it earns that promise the hard way.