The synopsis for the episode reads as follows:
Sick from her bullet wound and mistrustful of her colleagues, Nancy desperately needs an ally - but she can’t open up to Hayley for fear of putting them both in danger. When the police make a public appeal hoping to shake out the missing witness, Nancy is unexpectedly forced into the spotlight, leaving her exposed and bringing an old enemy out of the woodwork - Hayley’s ex-boyfriend, Shay Nash (Joe Absolom). Soon after Nancy receives a package, the contents of which, prove that someone is on to her. Nancy’s suspicions focus on her partner, Gunner, who watches her like a hawk. A colleague from London, DS Kevin O’Dowd (Rob James-Collier), sees her distress and wants to help. Nancy warns O’Dowd there’s a leak on the team - but can’t say more for fear of exposure. Meanwhile the murder investigation focuses on Frank Le Saux’s accountant, Theo Kettler (Rupert Procter). Already suspicious of Theo, Hayley questions her mother about the real nature of her father’s business, but Cherie Le Saux (Amanda Burton) is evasive. Isolated and anxious, Hayley turns for comfort to Le Saux family driver Darryl Quinn (Lorne MacFadyen). When a witness links Theo to a Newhaven garage suspected of drugs trafficking, police mount a surveillance operation. Pursuing her own dangerous investigation, Nancy finds herself at the same location – only to stumble into a second shocking murder.