Episode 1

The season opens with an ambush. A police convoy is hit, three officers are killed, and a protected witness is left fighting for his life. AC-12 turns its attention to the officer who led the convoy and walked away without a scratch: DI Lindsay Denton. But the arithmetic of the situation is uncomfortable from the start, and the episode is in no hurry to make it comfortable.

What follows is an investigation into an incident that should have been routine, conducted by people who can smell something wrong. The surviving officers are questioned, the records are pulled apart, and Denton's survival starts to look like a question in its own right. Arnott and Fleming work the case alongside Frank O'Neill, Vince Butler and the rest, and the atmosphere is tight. Nobody quite knows who knows what, and the show lets that uncertainty sit there until it starts to smell. Every answer leads to another question, and the paperwork keeps throwing up the same name. The episode went out in February 2014, and it set the tone for a second series that would spend far longer than the first circling the question of who in the ranks can be trusted.

Jed Mercurio wrote it, Douglas Mackinnon directed. Keeley Hawes arrives as Denton and immediately makes her the most interesting person in the room. Hawes gives her a quiet watchfulness that the whole season will build on. Mark Bonnar's Dryden, Michael Nardone's O'Neill, David Maybrick's Wallis, Antonio Magro's Butler, Allison McKenzie's Akers, Steve Toussaint's Mallick, Liz White's Dwyer, Martin Compston's Arnott and Vicky McClure's Fleming complete the cast.

This is high-stakes stuff from the first scene, and the series sets its own bar accordingly. The question running under everything is what you do with an officer who survives when everyone else did not. The episode is not asking us to decide yet. It is asking us to pay attention, and it makes paying attention easy.