DI Tom Mariner's home life is beginning to look more and more settled. There's talk of a move to the country, even kids. Mostly, of course, it's Anna doing the talking, and for once Mariner isn't running for the hills at the thought of commitment. But the quiet holiday season is shattered when, on the day of a community carol concert, an explosion rocks the centre of Birmingham. Running behind schedule, Tom and Anna are caught up in the aftermath of the event, but others are not so lucky, including DS Knox and his girlfriend. However, no one knows if the tragedy is accidental or another random act of terrorism. Meanwhile, as friends and colleagues struggle to deal with the after-effects of the explosion, an unexpected reunion with an old friend thrusts Mariner into the unofficial investigation of a violent double murder to which he is inextricably linked. Mariner enters a world of corruption where the boundaries of justice are blurred, making it impossible to distinguish between friend and foe.