Louise Gardiner (Zoe Telford) is an undercover officer from a nearby precint who infiltrates a gang of ruthless criminals, the Staffords, under the name Sarah Huddersfield. The gang is run by Terry (Peter Guinness) and Daniel Stafford (Bryan Dick) who are a father and son team that seem to be moving from robbery and other violoent crimes into major drug dealing. Gardiner is in place just before the son is released from prison with her mission to help bring down the gang.

Gardiners superior, DCI Wilson, has a grudge against the father after he was run over by an Austin Allegro during an attempt to stop a bank robbery and appears to have left Gardiner in place with little backup and disregard to her needs for protection during her undercover mission.