A monk lies dead in Snowdonia, a knife protruding from his throat. A young family is being held at gunpoint in a house in Wimbledon. The mission has begun.
A London Underground train is stationary in a tunnel, four hundred passengers trapped inside. All efforts to communicate with it have been met with silence.
DCI Ed Mallory has just started his day. The Met's top hostage negotiator - despite having been blinded thirteen years earlier - Mallory is about to discover that, today, an underground train is not the only thing on the line.