Detective Sergeant Nancy Devlin is a good cop with a dark secret - a loyalty to haulier and drugs trafficker Frank Le Saux, to whom she has been close since childhood. When a clandestine meeting ends in murder and Nancy is caught in the cross fire, her link to Frank suddenly risks being exposed.

In the wake of the latest killing, suspicion shifts to garage owner and Le Saux associate, Duncan Elliot. Visiting Elliot, Nancy spots Theo Kettler's missing car, and a tense chase ensues. When the driver escapes, Nancy and O'Dowd start to suspect Gunner of complicity. A vital piece of evidence is later recovered from the car, giving DCI Newman a breakthrough - but placing Nancy in even greater danger.